Precise construction method for suppressing powdering of ballastless track supporting layer and improving durability

Abstract

The application discloses a kind of precision construction methods of ballastless track supporting layer powder inhibition and durability promotion, comprising: base layer pretreatment, brushing powder inhibitor, construction high cohesive high impermeable polymer repair mortar, node special strengthening and effect test.Bottom layer inhibitor 25 ℃ viscosity≤10mPa·s, penetration depth≥3mm, bonding strength≥3.0MPa, realize deep penetration consolidation;Surface layer mortar 2h compressive strength≥15.0MPa, 28d shrinkage≤0.10%, bonding strength≥2.5MPa and cohesive failure, form rapid hardening, low shrinkage, high impermeable protective layer.Two layers of synergy from root block "powder-water intrusion" vicious cycle, single work point operation≤90 minutes, adapt high-speed rail window period, freeze-thaw resistance≥300 times, secondary disease incidence rate is reduced by more than 90%.The application solves the problems of interface cracking, long-term poor, etc., realizes deep repair and surface layer strengthening precision construction and nondestructive quality control closed loop.

Description

Technical Field

[0001] This invention relates to a construction method, and more particularly to a precise construction method for inhibiting pulverization and improving the durability of ballastless track support layers. Background Technology

[0002] The ballastless track support layer is the core load-bearing structure of a high-speed railway track system. It directly bears the dynamic load of high-speed trains transmitted from the sleepers and evenly transfers it to the roadbed or bridge foundation. Its strength, stability, and durability are directly related to the smoothness of the track and the safety of train operation. Currently, my country's high-speed railways widely use cast-in-place concrete support layers for ballastless tracks. As the "bottom foundation" of the track system, it undertakes the key functions of distributing loads, leveling the foundation, and protecting the substructure. However, during long-term service, the support layer concrete is subjected to the coupled influence of multiple environmental and load factors, such as freeze-thaw cycles, rainwater erosion, salt corrosion, train dynamic load vibration, and alternating wet and dry conditions. Typical defects such as surface pulverization, microcrack development, strength reduction, and local spalling are common. More prominently, the loose surface and microcracks formed by pulverization provide rapid intrusion channels for moisture and harmful ions such as chloride and sulfate, accelerating the failure of internal cement paste bonding and aggregate stripping, forming a vicious cycle of "pulverization-water intrusion-more severe pulverization." In severe cases, it can even lead to the loosening of the support layer structure, threatening the overall stability of the track system.

[0003] Currently, the technical solutions for repairing the pulverization of the support layer of ballastless track are mainly divided into three categories, and all of them have problems such as incomplete repair, insufficient adaptability, or disruption to operation:

[0004] The first type is the localized chiseling and repair solution. This involves manually or using small tools to remove the powdery and loose areas of the supporting layer, cleaning the base layer, applying an interface agent, and then applying layers of ordinary cement mortar or polymer-modified mortar to achieve localized filling and repair. This type of solution requires destructive removal of the deteriorated area, which can easily disturb the track's geometric accuracy and requires additional calibration later. The shrinkage deformation coefficient of the repair mortar differs greatly from that of the original concrete, making it prone to secondary cracking. Furthermore, the natural curing period is as long as 3-7 days, which is completely unsuitable for the rapid construction needs during the track maintenance window of the operating line.

[0005] The second type is the surface hydrophobic protection solution, which uses traditional silane-based impregnating agents applied to the surface of the supporting layer by spraying or rolling to form a surface hydrophobic layer that blocks water intrusion. This solution can only act on the concrete surface, with a penetration depth of less than 1mm, and cannot fill internal capillary pores and microcracks. It has no repair effect on deep, loose areas; moreover, it has strict requirements for the dryness of the substrate (moisture content ≤8%), the pretreatment is time-consuming, the hydrophobic effect is rapidly diminished by freeze-thaw cycles and ultraviolet radiation, and the durability is less than 5 years.

[0006] The third type is high-pressure grouting reinforcement, which targets pulverization accompanied by cracks. It employs a "drilling-cleaning-grouting-sealing" process, injecting cement-based or epoxy-based grout into the support layer to fill gaps and loose areas. This type of solution is cumbersome, requiring large equipment such as drilling machines and grouting pumps, and operating space is limited in the track area; grouting pressure control is stringent, easily leading to grout waste or uneven filling; it can only treat localized cracks and cannot cover large areas of pulverization, has poor adaptability to mild / moderate pulverization, and is costly and inefficient.

[0007] The related patented technologies in this field also have the aforementioned limitations. For example, patent CN202211358568.1 discloses a method for treating the pulverization of the support layer of ballastless track in high-speed railway operation. This method still requires cutting and chiseling away the support layer at the bottom of the track slab, which poses a risk of disturbing the track structure. Moreover, the non-film-forming anti-stripping agent used can only increase the surface strength by about 2MPa, with limited penetration depth, and cannot achieve deep consolidation. At the same time, this method still requires the erection of formwork and pouring for curing, and the operation time at a single work point still exceeds 120 minutes, which cannot meet the requirements of shorter track maintenance windows. For example, patent CN108751881A discloses a material and method for repairing the pulverized base plate of high-speed railway ballastless track. This method still requires the complete removal of the pulverized part, which is a destructive repair. Moreover, its repair material is only a single surface repair mortar, without a deep penetration and consolidation process, and cannot repair the internal micro-cracks and pores. After repair, there are still channels for harmful media to invade, and the risk of disease recurrence is high. At the same time, the early strength of the repair material of this method is insufficient, with a strength of only 5MPa after 1 hour, which cannot meet the strength requirements for rapid restoration of traffic during track maintenance windows.

[0008] In summary, the existing technologies share the following common shortcomings:

[0009] 1. Limited and fragmented functionality: Existing technologies often focus on a single repair objective. Localized chiseling and repair only address surface filling, surface hydrophobic protection only focuses on preventing water seepage, and high-pressure grouting reinforcement only targets crack treatment. None of these can simultaneously meet the comprehensive needs of deep structural reinforcement and efficient construction during the window period. Multiple layers of construction are required to cover multiple defects, resulting in cumbersome processes, high repeated investment costs, and the potential for problems such as "repairing the surface but neglecting the deeper layers" or "treating cracks but failing to prevent powdering."

[0010] 2. Inadequate material performance: Traditional repair mortars have high viscosity and poor compatibility with the original concrete, and differences in shrinkage deformation can easily lead to secondary cracking; silane impregnating agents have a penetration depth of less than 1mm, failing to reach deep, loose areas; the fluidity and curing speed of grouting materials are difficult to balance, resulting in either incomplete filling or easy clogging of pipes. All types of materials suffer from insufficient bond strength (mostly below 2MPa) and weak resistance to freeze-thaw cycles, resulting in short-lived repair effects that easily fail after 1-2 freeze-thaw seasons.

[0011] 3. Poor construction adaptability: Existing processes either rely on large equipment or involve cumbersome procedures, which restrict operation in the narrow working space of the track; solutions such as local chiseling and repair, high-pressure grouting and other methods have low construction efficiency per working surface and require more than 180 minutes of track maintenance window time, which is difficult to adapt to the regular track maintenance window period of 90-240 minutes; manual cleaning, painting and other links have a large workload, high overall cost and prominent safety risks.

[0012] 4. Inadequate quality control: Existing technologies lack unified and precise construction standards. Key indicators such as material usage, number of coats, and grouting pressure are all controlled by manual experience without quantitative standards. Quality inspections are mostly destructive sampling, which cannot comprehensively assess the repair effect, resulting in poor consistency in repair quality and easy occurrence of substandard local repairs.

[0013] 5. Insufficient long-term effectiveness: The various technical aspects operate independently, failing to form an integrated protection system encompassing "deep repair - surface reinforcement - node sealing - quality control closed loop." This only temporarily alleviates surface damage and cannot fundamentally break the vicious cycle of "pulverization - water intrusion - wear - more severe pulverization." The improvement in structural density and surface protection after repair is limited, with weak resistance to chloride ion and sulfate corrosion and abrasion, resulting in a high recurrence rate and ineffective control of life-cycle maintenance costs.

[0014] Therefore, there is an urgent need to develop an integrated technology that combines precise adaptation to disease conditions, deep repair and enhancement, and efficient construction during the window period to solve the above problems. Summary of the Invention

[0015] To address the shortcomings of existing technologies, this invention discloses a precise construction method for inhibiting pulverization and improving the durability of ballastless track support layers. The technical solution is as follows: A dual-layer synergistic repair system for ballastless track support layers, characterized by comprising:

[0016] The bottom layer is a low-viscosity reactive powdering inhibitor that can penetrate into the capillary pores of the support layer and solidify in situ, used to seal deep moisture and ion intrusion channels and solidify the loose layer.

[0017] The surface layer is a fast-hardening, low-shrinkage, high-adhesion polymer repair mortar that covers the bottom layer to form a dense protective layer that resists traffic loads and environmental erosion.

[0018] The bottom and top layers are chemically compatible and form an integrated synergistic structure of "deep consolidation-surface protection" through interfacial chemical bonding to block the vicious cycle of "pulverization-water intrusion".

[0019] Preferably, the powdering inhibitor is a reactive composite system with a viscosity of ≤10 mPa·s at 25℃, a penetration depth of ≥3 mm, a bond strength with concrete of ≥3.0 MPa, and is characterized by cohesive failure within the substrate; the repair mortar is a polymer-modified cement-based composite material with a 2-hour compressive strength of ≥15.0 MPa, a 28-day shrinkage rate of ≤0.10%, a 28-day bond strength of ≥2.5 MPa, and is characterized by cohesive failure within the concrete.

[0020] Preferably, the powdering inhibitor is composed of low-viscosity epoxy resin, silane coupling agent, nano-reinforcing filler, and composite curing accelerator, and by weight, it comprises: 100 parts of bisphenol A type epoxy resin, 5-15 parts of γ-aminopropyltriethoxysilane, 2-10 parts of nano-silica, and 30-40 parts of modified aliphatic amine curing agent; the repair mortar is composed of polymer emulsion, high-strength silicate cement, graded quartz sand, composite expansion agent, retarder and accelerator, and water-retaining agent, and by weight, it comprises: 120-180 parts of acrylate copolymer emulsion, 350-450 parts of P·II 52.5 grade silicate cement, 400-500 parts of graded quartz sand, 20-40 parts of U-type expansion agent, 3-8 parts of retarder and accelerator compounded with tartaric acid and sodium sulfate in a 1:4 ratio, and 0.5-2 parts of hydroxypropyl methylcellulose.

[0021] This invention also discloses a precise construction method for suppressing pulverization and improving the durability of ballastless track support layers using the aforementioned dual-layer synergistic repair system, characterized by comprising the following steps:

[0022] Base treatment: Clean and lightly grind the surface of the supporting layer to remove loose layers;

[0023] Penetration reinforcement: Apply the chalking inhibitor, controlling its dosage and penetration depth, and let it stand until surface dry;

[0024] Surface repair: Apply the repair mortar in layers, controlling its thickness and construction time, to form a repair layer;

[0025] Node reinforcement: For stress concentration areas in the support layer, increase the amount of the powdering inhibitor and / or increase the thickness of the repair mortar and compact and seal it;

[0026] Performance verification: At predetermined time points after construction, the key performance indicators of the repair layer are tested using non-destructive or minimal-destructive methods to form a quality control closed loop;

[0027] The construction method described herein has a total operation time of ≤90 minutes per work site, which is suitable for the high-speed rail operation window period.

[0028] Preferably, the base treatment further includes:

[0029] S1-1: Use a high-pressure blower with a pressure ≥0.8MPa and a wire brush to remove floating dust, loose debris and oil stains from the surface of the support layer;

[0030] S1-2: Lightly grind the severely pulverized areas using a micro angle grinder, with a grinding depth of ≤5mm, to remove the loose surface layer and expose the solid base surface;

[0031] S1-3: Level the base surface for areas with localized peeling depth ≥5mm;

[0032] S1-4: Test the moisture content of the base layer to ensure that the moisture content within 5mm of the surface layer is ≤10%, and the construction environment meets the requirements of temperature -10℃~35℃ and no strong winds or rainfall.

[0033] Preferably, the penetration reinforcement further includes:

[0034] S2-1: Mix the powdering inhibitor according to the product instructions, and stir at high speed with a hand-held electric mixer for 3-5 minutes until uniform;

[0035] S2-2: Use a combination of brush and roller for application. First, apply one coat evenly with a brush to ensure that the material penetrates into micro-cracks and pores.

[0036] S2-3: Apply another coat using a roller in a crisscross pattern, using a 45° angled brushing path when painting vertical surfaces;

[0037] S2-4: Control the total dosage of powdering inhibitor within the range of 0.6-0.8 kg / m²;

[0038] S2-5: After application, let stand for 15-20 minutes until the material is surface dry before proceeding with subsequent construction.

[0039] Preferably, the surface repair further includes:

[0040] S3-1: Add water to the repair mortar at a powder-to-water ratio of 5:1 to 5:1.2, and stir with a hand-held electric mixer for 5 minutes until it is uniform, free of lumps, and has suitable fluidity;

[0041] S3-2: Apply the coating in layers using a trowel. The first thin layer serves as an interface transition layer, with a thickness controlled within the range of 1-2mm, to ensure full adhesion with the underlying chalking inhibitor.

[0042] S3-3: Before the first layer sets, apply the second layer to the designed thickness within 1 hour. The total thickness should be adjusted to 3-8mm depending on the degree of surface damage. For the node areas identified in step S4-1, the total thickness of the repair mortar should be increased to 8-10mm in this step.

[0043] S3-4: When applying, scrape along the longitudinal direction of the track to ensure that the surface is flat and flush with the original support layer surface, with no obvious seams;

[0044] S3-5: The mixed repair mortar should be used within 30 minutes, and the second layer should be applied before initial setting.

[0045] Preferably, the node reinforcement further includes:

[0046] S4-1: Identify and locate the stress concentration area at the junction of the support layer and the base plate, and under the sleeper;

[0047] S4-2: Implement a double-coating process for the bottom layer in the node area. This double coating is performed in step S2, increasing the number of coats of the chalking inhibitor to 2, with the dosage controlled at 0.1 kg / m², and the width covering 5 cm on both sides of the node.

[0048] S4-3: Implement a surface thickening process in the node area. This thickening process is performed in step S3-3, increasing the thickness of the repair mortar to 8-10mm.

[0049] S4-4: After leveling in step S3-4, compact and seal the repair mortar along the joint direction to ensure that the gap is fully filled and there are no hollow areas.

[0050] Preferably, the effect verification further includes:

[0051] S5-1: Immediately after construction is completed, conduct visual and tapping inspections to check for any missed coatings, material accumulation, drips, or hollow areas.

[0052] S5-2: A re-inspection should be conducted 2 hours after construction to check whether the compressive strength of the repair mortar reaches ≥15.0MPa;

[0053] S5-3: A re-inspection shall be conducted 7 days after construction to test the 7-day compressive strength of the repair mortar ≥40.0MPa, the 7-day flexural strength ≥8.0MPa, and the bonding performance.

[0054] S5-4: A re-inspection shall be conducted 28 days after construction to test the penetration depth of the chalking inhibitor, the 28-day compressive strength of the repair mortar (≥55.0MPa), the 28-day flexural strength (≥12.0MPa), the 28-day bond strength, the 28-day shrinkage rate (≤0.10%), the alkali resistance, and the relative dynamic modulus of elasticity after 300 freeze-thaw cycles (≥60%) with a mass loss rate (≤5%).

[0055] Step S5 forms a non-destructive quality control closed loop.

[0056] The present invention also discloses the application of the above-mentioned double-layer repair system in the treatment of pulverization and / or spalling defects in the support layer of ballastless track.

[0057] Beneficial effects

[0058] Compared with existing technologies, this invention adopts a two-layer repair system of "deep penetration consolidation + surface structure reinforcement" and a matching precise construction method. Through the synergistic effect of the low-viscosity, high-penetration powdering inhibitor in the bottom layer and the fast-hardening, low-shrinkage, high-adhesion polymer repair mortar in the surface layer, combined with quantitatively controlled construction technology and a four-stage non-destructive quality control closed loop, it effectively solves the key technical problems in existing ballastless track support layer powdering repair technologies, such as single and fragmented functions, insufficient material performance, poor construction adaptability, rough quality control, and insufficient long-term effectiveness, and achieves the following beneficial effects:

[0059] 1. Achieved synergistic repair of deep and surface layers, eradicating the cycle of powdering and deterioration.

[0060] This invention utilizes a bottom-layer TK-LVE-GDZC type powdering inhibitor (viscosity ≤10 mPa·s at 25℃, penetration depth ≥3mm, and bond strength with concrete ≥3.0 MPa) to rapidly penetrate into the microcracks and capillary pores within the support layer under the drive of capillary action and concentration difference. It reacts chemically with cement hydration products to generate a three-dimensional silica-oxygen network structure in situ, achieving an integrated "penetration-filling-consolidation" process and sealing the channels for harmful media intrusion from the source. Simultaneously, the surface layer of TK-XB high-adhesion and high-permeability polymer repair mortar (compressive strength ≥15.0 MPa at 2h, bond strength ≥2.5 MPa at 28d, and cohesive failure within concrete, shrinkage rate ≤0.10% at 28d) rapidly forms a dense protective layer with high strength, high wear resistance, and high permeability. The dual-layer synergy fundamentally breaks the vicious cycle of "pulverization-water intrusion-more severe pulverization". After repair, the support layer can withstand freeze-thaw cycles ≥300 times, the chloride ion diffusion coefficient is no higher than that of the original concrete, the incidence of secondary defects is reduced by more than 90%, and the operation and maintenance cost throughout the entire life cycle is reduced by more than 50% compared with the existing technology.

[0061] 2. It enabled efficient construction during the skylight period, minimizing operational disruptions.

[0062] This invention optimizes the entire process of "base pretreatment → inhibitor application → mortar construction → joint reinforcement → effect inspection," utilizing the 15-20 minute surface drying characteristic of the base inhibitor and the 2-hour rapid hardening characteristic of the surface mortar (2-hour compressive strength ≥15.0 MPa). The total operation time for a single work site is ≤90 minutes. It eliminates the need for large equipment such as drilling, grouting, formwork, and pouring, and requires no long-term curing. It is perfectly suited for the regular maintenance window of high-speed rail (90-240 minutes). Compared with traditional methods such as chiseling and repair (curing for 3-7 days), high-pressure grouting (cumbersome process), and the patented method CN202211358568.1 (>120 minutes), it significantly improves construction efficiency and minimizes interference with the operating line.

[0063] 3. Solves industry pain points such as interface cracking and debonding, ensuring long-term structural stability.

[0064] This invention's surface repair mortar compensates for shrinkage with a composite expansion agent, toughens with a polymer emulsion, and optimizes the bulk density with graded quartz sand, resulting in a 28-day shrinkage rate ≤0.10%, coordinating deformation with existing concrete (shrinkage rate 0.02%-0.04%). Simultaneously, the residual active epoxy and amino groups on the surface of the cured bottom inhibitor undergo a cross-linking reaction with the polymer emulsion in the surface mortar, forming a chemical anchor. The 28-day bond strength (untreated) is ≥2.5 MPa, exhibiting cohesive failure within the concrete; after water immersion treatment, it is ≥1.5 MPa; and after 25 freeze-thaw cycles, it is ≥1.5 MPa, still exhibiting cohesive failure. Compared to the interface cracking and debonding problems easily encountered with traditional repair materials, this invention achieves a strong integration between the repair layer and the substrate, significantly improving long-term service stability.

[0065] 4. A closed-loop system of quantitative and precise construction and non-destructive quality control was achieved, ensuring consistent repair quality.

[0066] This invention establishes a five-dimensional collaborative control standard encompassing material dosage, penetration depth, coating / applying process, layer thickness, and performance indicators: inhibitor dosage is 0.6-0.8 kg / m², penetration depth ≥3 mm; total mortar layer thickness is 3-8 mm, with thickened joints to 8-10 mm; the entire construction process is conducted at temperatures ranging from -10℃ to 35℃ and a substrate moisture content ≤10%. Simultaneously, a four-stage non-destructive quality control system is established, including immediate testing, 2-hour re-testing, 7-day re-testing, and 28-day final testing. Testing indicators cover penetration depth, compressive strength, flexural strength, bond strength, shrinkage, alkali resistance, and frost resistance, and are implemented according to the Q / CR 659 standard. This replaces the traditional extensive approach relying on manual experience without quantitative standards, increasing the repair pass rate to over 98%.

[0067] 5. Enhanced protection of stress concentration areas, eliminating the risk of disease recurrence.

[0068] This invention addresses stress concentration areas such as the junction of the support layer and base plate, and below the sleepers, by designing a specialized reinforcement process: "double-coating the base layer (two coats, 0.1 kg / m, covering 5 cm on each side) + thickening and compacting the surface layer (8-10 mm, compacted and sealed along the joint)." This process allows the inhibitor to penetrate to a depth of over 5 mm in the joint area, increases the load-bearing cross-sectional area of ​​the mortar layer, and forms a full-section seal at the joint, completely blocking the path of moisture intrusion along weak points. Compared to the shortcomings of existing technologies, such as weak joint protection and easy recurrence of defects, this invention significantly improves the overall structural durability. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0070] Figure 2 This is a cross-sectional view of the dual-layer repair system architecture of the present invention. Detailed Implementation

[0071] All performance indicators involved in this invention were measured according to the following standard methods:

[0072] Viscosity: According to GB / T 10247-2008 "Methods for Viscosity Measurement", the viscosity was measured using a rotational viscometer (rotor number S21, rotation speed 60 rpm) at 25℃±0.5℃.

[0073] Penetration depth: Fluorescent tracer method was used. The chalking inhibitor was coated on the surface of C40 concrete blocks at a rate of 0.7 kg / m². After curing for 28 days at 23℃±2℃ and RH50%±5%, the blocks were cut perpendicular to the coated surface, and the fluorescence penetration depth was observed under a UV lamp (wavelength 365 nm). The average value of 5 measuring points was taken.

[0074] Bond strength: determined according to Appendix A of Q / CR 659 "Repair Mortar for High-Speed ​​Railway Concrete Structures", with a tensile speed of 1 mm / min, and the failure load and failure mode were recorded.

[0075] Shrinkage rate: determined according to the contact method in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", with specimen size of 40mm×40mm×160mm.

[0076] Freeze resistance: determined according to the rapid freezing method in GB / T 50082-2009, with the relative dynamic modulus and mass loss recorded every 25 cycles.

[0077] Chloride ion diffusion coefficient: determined according to the RCM method in GB / T 50082-2009.

[0078] For the sake of brevity, the low-viscosity reactive powdering inhibitor described in this invention will be referred to as "TK-LVE-GDZC type" and the polymer repair mortar as "TK-XB type". These designations are only used to refer to the specific material schemes of this invention and do not constitute additional limitations on the materials.

[0079] Example 1

[0080] A two-layer repair system for ballastless track support layers includes the following components:

[0081] 1. Overall System Structure

[0082] This embodiment provides a two-layer repair system for the support layer of ballastless track, consisting of a bottom layer of pulverization inhibitor and a surface layer of repair mortar. The bottom layer is a TK-LVE-GDZC type pulverization inhibitor, and the surface layer is a TK-XB high-adhesion, high-permeability polymer repair mortar. Through synergistic material composition, matching construction sequence, and interfacial chemical bonding, the two form a two-layer repair structure of "deep penetration and consolidation + surface structural reinforcement," aiming to fundamentally break the vicious cycle of "pulverization-water intrusion-more severe pulverization" in the support layer of ballastless track, and adapting to the rapid construction requirements during high-speed rail maintenance windows (90-240 minutes).

[0083] 2. Bottom layer: TK-LVE-GDZC type powdering inhibitor

[0084] 2.1 Material Composition and Preparation

[0085] The base material is a low-viscosity, high-permeability, reactive composite system designed based on concrete interface chemistry and capillary permeation principles. The core components and their mass distribution are as follows:

[0086] Low viscosity epoxy resin: Bisphenol A type epoxy resin (epoxy equivalent about 190 g / eq, viscosity at 25℃ about 8 mPa·s), 100 parts;

[0087] Silane coupling agent: γ-aminopropyltriethoxysilane (KH-550), 5-15 parts, preferably 8 parts;

[0088] Nano-reinforcing filler: Nano-silica (average particle size 20 nm, specific surface area ≥200 m² / g), 2~10 parts, preferably 5 parts;

[0089] Composite curing accelerator: 30-40 parts of a modified aliphatic amine (viscosity of about 15 mPa·s at 25℃) prepared by addition reaction of benzyl alcohol and nonylphenol glycidyl ether to triethylenetetramine, preferably 35 parts.

[0090] Preparation method: Add each component to the reaction vessel in sequence at room temperature, and stir at 500 r / min for 15 minutes until uniform and transparent to obtain the product.

[0091] Comparative studies show that if the amount of silane coupling agent is less than 5 parts, the bonding strength decreases to <2.5 MPa; if it is more than 15 parts, the system viscosity increases to >15 mPa·s, and the penetration depth is less than 2 mm. When the amount of nano silica is less than 2 parts, the resilience strength improvement rate is <15%; when it is more than 10 parts, the system storage stability deteriorates.

[0092] 2.2 Key performance indicators and their design basis

[0093] (1) Viscosity: ≤10 mPa·s at 25℃

[0094] The rotational viscometer method was used for the determination. The design was based on the fact that after the support layer pulverized, a large number of microcracks (10-100 μm wide) and capillary pores (0.1-10 μm in diameter) existed within the top 5 mm. According to the Washburn capillary permeability equation, the penetration depth is inversely proportional to the square root of the viscosity. When the viscosity is ≤10 mPa·s, the material can autonomously penetrate into the loose layer to a depth ≥3 mm within 15-20 minutes driven by capillary action and concentration gradient; if the viscosity is higher than 20 mPa·s, it can only cover the surface and cannot penetrate into the microcracks. Reverse experiments showed that using a control material with 25 mPa·s, the penetration depth was only 0.8 mm under the same conditions, failing to reach the deep pulverized zone.

[0095] (2) Penetration depth: ≥3 mm

[0096] Fluorescent tracer method was used to determine the penetration depth: the material was coated on the surface of a C40 concrete specimen, cured for 28 days, and then cut. The fluorescence penetration depth was observed under ultraviolet light. Design basis: the pulverization and deterioration depth of the support layer is usually 2-5 mm. A penetration depth ≥3 mm can ensure that the repair layer covers the main deteriorated areas and forms a continuous consolidation zone. If the penetration depth is <3 mm, the deep capillary pores and microcracks are not filled, and harmful media can still invade, shortening the disease recurrence cycle to 1-2 years.

[0097] (3) Bond strength with concrete: ≥3.0 MPa, and cohesive failure within the substrate.

[0098] The tensile bond strength was determined using the tensile bond strength method. Design basis: Train dynamic loads generate shear and pull-out stresses at the interface, with a measured peak value of approximately 2.5 MPa. A bond strength ≥3.0 MPa provides sufficient safety margin. More importantly, the failure mode must be cohesive failure within the substrate (i.e., failure occurs within the original concrete of the supporting layer or the repair layer, not at the interface), proving that the chemical bond strength is higher than the material's bulk strength. This product achieves this through a silane coupling agent: its ethoxy groups undergo a condensation reaction with the hydroxyl groups on the surface of cement hydration products (CSH, Ca(OH)2) to form Si-O-Si covalent bonds, while the amino groups participate in the curing of the epoxy resin, forming a "chemical anchor." Compared to the formulation without a silane coupling agent, the bond strength drops to 2.1 MPa and exhibits interfacial delamination.

[0099] (4) Improvement rate of concrete rebound strength after repair: ≥20%

[0100] Measured by the rebound method. Design basis: The design strength of the supporting layer is usually C30 - C40. After pulverization, the rebound strength can decrease by more than 30%. A strength increase of ≥20% after repair means restoring to near the original strength. The strengthening mechanism includes: nano - silica fills nano - scale pores and simultaneously promotes the high - cross - linked density curing of epoxy resin as a nucleation site, re - cementing the loose layer. For formulations without nano - fillers, the increase rate is only 12%.

[0101] (5)Freeze - thaw cycle resistance: ≥300 times

[0102] Measured by the rapid freezing method (qualified when the relative dynamic modulus ≥60% and the mass loss ≤5%). Design basis: China's high - speed rail lines span multiple climate zones. In cold regions, the annual freeze - thaw cycle can reach more than 100 times. 300 times is equivalent to a service life of 10 - 15 years. This product forms a continuous hydrophobic network through low - viscosity epoxy, blocking the transfer of freezing and swelling stress of water in pores. If the freeze - thaw resistance is less than 300 times, micro - cracks and spalling will appear in the repair layer after 2 - 3 winters in cold regions.

[0103] (6)Chloride ion diffusion coefficient: ≤ the original concrete

[0104] Measured by the RCM method. Design basis: Chloride ion intrusion is the main cause of steel bar corrosion and concrete deterioration. After this product penetrates and consolidates, it closes the capillary channels, reducing the chloride ion diffusion coefficient to 0.7 - 0.9 times that of the original concrete. If the diffusion coefficient is higher than that of the original concrete, the repair will instead accelerate ion transport, achieving the opposite effect.

[0105] 2.3 Curing characteristics and construction window

[0106] The surface - drying time of this product ≤4 h (25℃, RH 60%), and it takes 24 h to fully cure. However, in the construction method of this invention, after the bottom layer is painted, it only needs to be left standing for 15 - 20 min to reach surface - dry (no stickiness when touched by finger), and then the surface mortar construction can be carried out. This design is based on the concept of "function sharing": the bottom layer only needs to lose fluidity to provide a stable base surface, while the 2 - h rapid hardening of the surface mortar承担 the temporary bearing function during the skylight period. The two work together, ensuring both the sufficiency of the bottom - layer penetration and consolidation and the rapid restoration of traffic during the skylight period. <000022​​​​​​​​​Polymer emulsion: Acrylic ester copolymer emulsion (50% solids content, glass transition temperature -10℃), 150 parts;

[0111] High-strength silicate cement: P·II 52.5 grade, 400 parts;

[0112] Graded quartz sand: 40-70 mesh and 70-140 mesh mixed at a mass ratio of 3:7, 450 parts;

[0113] Composite expanding agent: U-shaped expanding agent (limited expansion rate ≥0.02%), 30 parts;

[0114] Retarding and early-strength agent: Tartaric acid and sodium sulfate are mixed at a ratio of 1:4, 5 parts;

[0115] Water-retaining agent: 1 part of hydroxypropyl methylcellulose (viscosity 400 mPa·s).

[0116] The dry powder components are pre-mixed, and polymer emulsion and an appropriate amount of water (powder-to-water ratio 5:1 to 5:1.2) are added on-site and stirred until uniform.

[0117] 3.2 The irreplaceable nature and importance of the above proportions

[0118] This formula has been optimized through extensive experimentation. Each component is indispensable, and the proportion range has strict critical limits, as detailed below:

[0119] (1) The irreplaceability of polymer emulsions

[0120] The acrylate copolymer emulsion (150 parts) is the core functional component of this formulation. Its functions include: ① forming a continuous polymer film during cement hydration, interpenetrating with the cement paste, significantly improving bond strength and flexural strength; ② reducing the elastic modulus, buffering shrinkage stress, and preventing interfacial cracking; ③ filling capillary pores, improving impermeability and frost resistance. If the polymer emulsion is omitted, the resulting material is pure cement mortar, with a 2-hour compressive strength of only 5-8 MPa, a 28-day bond strength <1.5 MPa, and a shrinkage rate >0.20%, failing to meet any of the required indicators. If the emulsion dosage is less than 100 parts, the film formation is discontinuous, and the bond strength and frost resistance decrease significantly; if it is more than 200 parts, the material viscosity is too high, workability is poor, and early strength is reduced.

[0121] (2) The necessity of high-strength silicate cement

[0122] P·II 52.5 grade cement (400 parts) was chosen instead of ordinary 42.5 grade cement because it has a higher C3S and C3A content, resulting in faster early hydration, which is key to achieving a compressive strength of ≥15 MPa after 2 hours. If 42.5 grade cement were used instead, the compressive strength after 2 hours would only be 10-12 MPa under the same mix proportions, which would not meet the requirements for opening to traffic during the maintenance window. When the cement content is less than 350 parts, there is insufficient cementitious material, and the strength does not meet the standard; when it is more than 450 parts, the shrinkage rate increases, and cracking is more likely.

[0123] (3) Optimization design of graded quartz sand

[0124] By mixing 40-70 mesh and 70-140 mesh sand in a 3:7 ratio, close packing of particles is achieved, minimizing porosity. This gradation design reduces water demand by approximately 15% compared to single-size sand, thereby lowering the water-cement ratio and improving strength and impermeability. If single-size sand (such as using only 70-140 mesh fine sand) is used, water demand increases, 28-day compressive strength decreases by approximately 20%, and shrinkage increases to over 0.15%.

[0125] (4) The key role of composite expansion agent

[0126] The U-shaped expansive agent (30 parts) generates ettringite, causing volume expansion (limited expansion rate ≥0.02%) to compensate for the autogenous shrinkage and drying shrinkage of the cement paste. In this formulation, without the expansive agent, the 28-day shrinkage rate is as high as 0.18%-0.22%, far exceeding the requirement of ≤0.10%, and cracks will inevitably appear at the interface 30-60 days after repair. If the amount of expansive agent is less than 15 parts, the compensation is insufficient, and the shrinkage rate is still >0.12%; if it is more than 45 parts, excessive expansion will lead to internal micro-cracks and a decrease in strength.

[0127] (5) Synergistic effect of retarder and early strength agent

[0128] Tartaric acid and sodium sulfate are mixed in a 1:4 ratio, with a total dosage of 5 parts. This achieves a balance between workability and early strength: tartaric acid delays initial setting by approximately 30 minutes, ensuring a suitable application window for layered application; sodium sulfate promotes C3S hydration to form ettringite, providing early strength within 2 hours. If tartaric acid is omitted, the initial setting time is shortened to 10 minutes, making layered application impossible; if sodium sulfate is omitted, the 2-hour compressive strength drops to 8-10 MPa. A deviation from the 1:4 ratio results in either excessive retardation or insufficient early strength.

[0129] (6) Functions of water-retaining agents

[0130] Hydroxypropyl methylcellulose (1 part) improves the water retention and anti-sagging properties of the mortar, preventing excessive water absorption by the substrate and thus insufficient hydration. If the water-retaining agent is omitted, moisture will rapidly escape from the interface when applying to a dry substrate, reducing the bond strength by approximately 30% and making it prone to delamination.

[0131] 3.3 Key performance indicators and their design basis

[0132] (1) Compressive strength and flexural strength

[0133] Requirements: Compressive strength ≥ 15.0 MPa at 2 h, ≥ 25.0 MPa at 1 d, ≥ 40.0 MPa at 7 d, and ≥ 55.0 MPa at 28 d; corresponding flexural strength ≥ 5.0 MPa at 2 h, ≥ 6.0 MPa at 1 d, ≥ 8.0 MPa at 7 d, and ≥ 12.0 MPa at 28 d.

[0134] Design Basis: The compressive stress on the surface of the support layer is approximately 10-12 MPa when a high-speed train passes. A 2-hour compressive strength ≥ 15.0 MPa ensures immediate resumption of traffic after the maintenance window without damage. The measured values ​​of the above mix proportions are: 2-hour compressive strength 16.2 MPa, 1-day compressive strength 28.5 MPa, 7-day compressive strength 45.3 MPa, and 28-day compressive strength 62.8 MPa; corresponding flexural strengths are 5.8, 7.2, 9.1, and 14.5 MPa, respectively, all meeting the requirements. If the 2-hour compressive strength is < 15 MPa (e.g., 8-10 MPa), the repair layer will rapidly fail after traffic resumes.

[0135] (2) Bond strength and failure mode

[0136] Requirements: 28-day bond strength ≥2.5 MPa in the untreated state and cohesive failure of concrete, ≥1.5 MPa after water immersion treatment, and ≥1.5 MPa after 25 freeze-thaw cycles and still cohesive failure of concrete.

[0137] Design Basis: This product exhibits chemical compatibility with the underlying inhibitor—after the underlying layer cures, residual active epoxy and amino groups on the surface undergo a cross-linking reaction with the polymer emulsion in the surface mortar, forming a "chemical anchor." Actual measured values ​​for this formulation are: untreated 3.2 MPa (cohesive failure), water-treated 2.1 MPa, and after 25 freeze-thaw cycles 1.9 MPa (cohesive failure). If the bond strength is insufficient or the failure mode is interfacial delamination, the repair layer is prone to complete detachment under dynamic loads.

[0138] (3) Shrinkage rate: 28-day shrinkage rate ≤ 0.10%

[0139] Design Basis: The shrinkage rate of ordinary cement mortar is approximately 0.15%-0.30%, which differs significantly from that of existing concrete (shrinkage rate 0.02%-0.04%), making it prone to interfacial cracking. This mix design compensates for shrinkage through an expansive agent, reduces moisture evaporation through a polymer emulsion, and lowers water demand through graded sand. Actual measured shrinkage rate after 28 days is only 0.06%. If the shrinkage rate is greater than 0.10%, the interfacial tensile stress after 28 days can reach 2-3 MPa, exceeding the bond strength and causing delamination.

[0140] (4) Alkali resistance: No cracking or peeling

[0141] Design Basis: The pH of the pore fluid in the supporting concrete layer is >12, and the repair material must be alkali-resistant. In this formulation, the acrylic emulsion does not saponify in an alkaline environment, and the low water-to-binder ratio (0.18-0.22) forms a dense structure, preventing alkali penetration. Actual testing showed no cracking or peeling after 7 days of immersion in saturated Ca(OH)₂ solution.

[0142] (5) Freeze-thaw resistance: After 300 freeze-thaw cycles, the relative dynamic modulus of elasticity is ≥60%, and the mass loss rate is ≤5%.

[0143] Design Basis: Same as the base layer, ensuring long-term service under freeze-thaw conditions. This formulation, after 300 freeze-thaw cycles, showed a relative dynamic modulus of 78% and a mass loss of 1.2%. Mechanism of Action: Polymer film fills capillary pores, reducing water absorption; the expanding agent reduces internal micro-cracks, preventing the propagation of freeze-thaw damage.

[0144] 3.4 Synergistic Effect with the Underlying Layer

[0145] The core of this bilayer system lies in functional complementarity and chemical compatibility:

[0146] Complementary functions: The bottom layer is responsible for "blocking"—penetrating and consolidating deep, loose areas to seal capillary channels; the top layer is responsible for "protection"—providing a high-strength, highly wear-resistant, and highly impermeable protective layer. When the bottom layer is used alone, its surface wear resistance is insufficient, and it will gradually wear down under long-term train friction and rain erosion; when the top layer is used alone, deep micro-cracks are not filled, and harmful media can invade from the sides or weak areas of the bottom layer.

[0147] Chemical compatibility: After the bottom layer cures, the surface-active groups undergo a cross-linking reaction with the surface polymer emulsion, forming chemical bonds. Tests show that the interfacial bond strength of the two-layer system (3.2 MPa) is 78% higher than that of the surface mortar directly applied to untreated concrete (1.8 MPa), and the bond strength retention rate is ≥90% after 300 freeze-thaw cycles.

[0148] 4. Verification of the overall system effectiveness

[0149] The two-layer repair system of this embodiment was used to repair the actual pulverized support layer (original resilience strength 30.5 MPa). Testing showed that:

[0150] The bottom layer inhibitor penetrates to a depth of 3.8 mm, completely sealing capillary pores and microcracks;

[0151] After repair, the rebound strength increased to 36.8 MPa, an improvement of 20.7% (compared to 30.5 MPa before repair).

[0152] The interfacial bond strength at 28 days was 3.2 MPa, and the failure mode was cohesive failure of concrete.

[0153] After 300 freeze-thaw cycles, the mass loss was only 1.2%, the relative dynamic modulus was 82%, and there were no visible cracks or spalling.

[0154] The chloride ion diffusion resistance coefficient is 0.85 times that of the original concrete, which is superior to that of the original concrete;

[0155] The total repair time for a single work site is 82 minutes, which is fully compatible with the regular maintenance window for high-speed rail (90-240 minutes).

[0156] 5. Comparative verification (reverse example)

[0157] To demonstrate the critical necessity of the key indicators, the following comparative groups were set up (all using the construction method of this embodiment, only the material parameters were changed):

[0158]

[0159] The above comparison fully demonstrates that the performance index range defined by the present invention is a critical necessary condition for achieving "deep repair + long-term durability". Deviation from any key index will lead to a significant decrease in the repair effect.

[0160] Example 2 (Lower Limit Ratio Example)

[0161] This embodiment provides a two-layer repair system for the support layer of ballastless track. The components of the bottom powdering inhibitor and the surface repair mortar are both at the lower limit of the ratio range described in Example 1, in order to verify the performance compliance under the boundary conditions of the ratio.

[0162] 1. Bottom layer: Low-limit ratio powdering inhibitor

[0163] 1.1 Material Composition and Preparation

[0164] Weigh the following components by weight: 100 parts of bisphenol A type epoxy resin (epoxy equivalent approximately 190 g / eq, viscosity at 25℃ approximately 8 mPa·s); 5 parts of γ-aminopropyltriethoxysilane (KH-550); 2 parts of nano-silica (average particle size 20 nm, specific surface area ≥200 m² / g); and 30 parts of modified aliphatic amine curing agent (viscosity at 25℃ approximately 15 mPa·s). Preparation method: Add each component sequentially to the reactor at room temperature and stir at 500 r / min for 15 minutes until uniform and transparent to obtain the product.

[0165] 1.2 Key Performance Testing

[0166] The tests were conducted according to the standards specified in the "Key Performance Test Methods" section of this manual, and the results are as follows: Viscosity at 25℃ is 7.2 mPa·s, meeting the requirement of ≤10 mPa·s; penetration depth is 3.2 mm, meeting the requirement of ≥3 mm; bond strength with concrete is 3.1 MPa, and the failure mode is cohesive failure within the substrate, meeting the requirement of ≥3.0 MPa and cohesive failure; the rebound strength improvement rate of the repaired concrete is 21.3%, meeting the requirement of ≥20%; freeze-thaw resistance reaches 315 cycles, and after 315 freeze-thaw cycles, the relative dynamic modulus of elasticity is 68% and the mass loss rate is 3.8%, meeting the requirement of ≥300 cycles; the chloride ion diffusion coefficient is 0.88 times that of the original concrete, meeting the requirement of not exceeding the original concrete.

[0167] 2. Surface layer: Low-ratio repair mortar

[0168] 2.1 Material Composition and Preparation

[0169] Weigh the following components by weight (dry powder pre-mixed, polymer emulsion and appropriate amount of water added on site): 120 parts of acrylate copolymer emulsion (50% solid content, glass transition temperature -10℃); 350 parts of P·II 52.5 grade silicate cement; 400 parts of graded quartz sand (40-70 mesh and 70-140 mesh mixed at a mass ratio of 3:7); 20 parts of U-shaped expansion agent (limited expansion rate ≥0.02%); 3 parts of retarder and accelerator (tartaric acid: sodium sulfate = 1:4); 0.5 parts of hydroxypropyl methylcellulose (viscosity 400 mPa·s). During construction, control the powder-to-water ratio at 5:1.1 and mix with a hand-held electric mixer for 5 minutes until homogeneous.

[0170] 2.2 Key Performance Testing

[0171] The results, tested according to standard methods, are as follows: Regarding compressive strength, the 2-hour compressive strength is 15.3 MPa, the 1-day compressive strength is 25.8 MPa, the 7-day compressive strength is 41.2 MPa, and the 28-day compressive strength is 56.7 MPa, meeting the requirements of ≥15.0 MPa, ≥25.0 MPa, ≥40.0 MPa, and ≥55.0 MPa respectively. Regarding flexural strength, the 2-hour flexural strength is 5.2 MPa, the 1-day flexural strength is 6.3 MPa, the 7-day flexural strength is 8.1 MPa, and the 28-day flexural strength is 12.3 MPa, meeting the requirements of ≥5.0 MPa, ≥6.0 MPa, ≥8.0 MPa, and ≥12.0 MPa respectively. The 28-day bond strength is 2.6 MPa in the untreated state and exhibits cohesive failure, meeting the requirement of ≥2.5 MPa and cohesive failure; after water immersion treatment, it is 1.6 MPa, meeting the requirement of ≥1.5 MPa. The required MPa is 1.5 MPa after 25 freeze-thaw cycles, indicating cohesive failure of the concrete, meeting the requirement of ≥1.5 MPa and cohesive failure. The 28-day shrinkage rate is 0.09%, meeting the requirement of ≤0.10%. In the alkali resistance test, there was no cracking or peeling after immersion in saturated Ca(OH)2 solution for 7 days, meeting the requirements. Regarding frost resistance, after 300 freeze-thaw cycles, the relative dynamic modulus of elasticity is 62%, and the mass loss rate is 4.8%, meeting the requirements of ≥60% and ≤5% respectively. In summary, all properties of the surface repair mortar with the low-limit mix ratio meet the index requirements.

[0172] Example 3 (High Limit Ratio Example)

[0173] This embodiment provides a two-layer repair system for ballastless track support layers. The components of both the bottom layer powdering inhibitor and the surface repair mortar are at the high limit of the proportion range described in Example 1, aiming to verify the performance compliance and process feasibility under the boundary conditions of this proportion. 1. Bottom layer: High-limit proportion powdering inhibitor

[0174] 1.1 Material Composition and Preparation

[0175] Weigh the following components by weight: 100 parts of bisphenol A type epoxy resin (epoxy equivalent approximately 190 g / eq, viscosity at 25°C approximately 8 mPa·s); 15 parts of γ-aminopropyltriethoxysilane (KH-550); 10 parts of nano-silica (average particle size 20 nm, specific surface area ≥200 m² / g); and 40 parts of modified aliphatic amine curing agent (viscosity at 25°C approximately 15 mPa·s). The preparation method is the same as in Example 3.

[0176] 1.2 Key Performance Testing

[0177] According to standard testing methods, the results are as follows: the viscosity at 25℃ is 9.8 mPa·s, meeting the requirement of ≤10 mPa·s; the penetration depth is 4.5 mm, meeting the requirement of ≥3 mm; the bond strength with concrete is 3.8 MPa, and the failure mode is cohesive failure within the substrate, meeting the requirement of ≥3.0 MPa and cohesive failure; the rebound strength improvement rate of the repaired concrete is 24.6%, meeting the requirement of ≥20%; the freeze-thaw resistance reaches 350 cycles, and after 350 freeze-thaw cycles, the relative dynamic modulus of elasticity is 72% and the mass loss rate is 2.9%, meeting the requirement of ≥300 cycles; the chloride ion diffusion resistance coefficient is 0.79 times that of the original concrete, meeting the requirement of not exceeding the original concrete. It should be noted that the viscosity in this embodiment is close to the upper limit of 10 mPa·s, indicating that it is not advisable to further increase the amount of silane coupling agent or curing agent, but all performance indicators meet the requirements.

[0178] 2. Surface layer: High-ratio repair mortar

[0179] 2.1 Material Composition and Preparation

[0180] Weigh the following components by weight: 180 parts acrylate copolymer emulsion; 450 parts P·II 52.5 grade silicate cement; 500 parts graded quartz sand; 40 parts U-shaped expanding agent; 8 parts retarder / accelerator (tartaric acid: sodium sulfate = 1:4); 2 parts hydroxypropyl methylcellulose. During construction, control the powder-to-water ratio at 5:1.0 (reduce the amount of water added appropriately due to the increased emulsion volume), and stir until homogeneous.

[0181] 2.2 Key Performance Testing

[0182] The results, tested according to standard methods, are as follows: Regarding compressive strength, the 2-hour compressive strength is 17.8 MPa, the 1-day compressive strength is 30.2 MPa, the 7-day compressive strength is 48.5 MPa, and the 28-day compressive strength is 68.3 MPa, meeting the requirements of ≥15.0 MPa, ≥25.0 MPa, ≥40.0 MPa, and ≥55.0 MPa respectively. Regarding flexural strength, the 2-hour flexural strength is 6.4 MPa, the 1-day flexural strength is 8.1 MPa, the 7-day flexural strength is 10.2 MPa, and the 28-day flexural strength is 15.8 MPa, meeting the requirements of ≥5.0 MPa, ≥6.0 MPa, ≥8.0 MPa, and ≥12.0 MPa respectively. The 28-day bond strength is 3.5 MPa in the untreated state and exhibits cohesive failure, meeting the requirement of ≥2.5 MPa and cohesive failure; after water immersion treatment, it is 2.3 MPa, meeting the requirement of ≥1.5 MPa. The required MPa is 2.1 MPa after 25 freeze-thaw cycles, indicating cohesive failure of the concrete, meeting the requirement of ≥1.5 MPa and cohesive failure. The 28-day shrinkage rate is 0.05%, meeting the requirement of ≤0.10%. In the alkali resistance test, there is no cracking or peeling after immersion in saturated Ca(OH)2 solution for 7 days, meeting the requirements. Regarding frost resistance, after 300 freeze-thaw cycles, the relative dynamic modulus of elasticity is 85%, and the mass loss rate is 0.9%, meeting the requirements of ≥60% and ≤5% respectively. It should be noted that when the emulsion dosage reaches 180 parts, the mortar viscosity increases, and the troweling pressure needs to be appropriately increased during construction. When the expansion agent dosage reaches 40 parts, the curing conditions need to be strictly controlled to avoid excessive expansion, but the above-mentioned high limit ratios are still within the workable range, and all performance indicators meet the requirements.

[0183] Example 4

[0184] A Precision Construction Method for Inhibiting Powdering and Improving Durability of Ballastless Track Support Layer

[0185] This embodiment employs the dual-layer repair system described in the previous embodiment (bottom layer TK-LVE-GDZC type chalking inhibitor and top layer TK-XB high-adhesion and high-permeability polymer repair mortar), following a five-step process: "base layer pretreatment → application of chalking inhibitor → surface construction of repair mortar → special reinforcement of joints → effect inspection," to repair a chalking defect section of the ballastless track support layer of a high-speed railway line. The construction environment temperature was 15℃, humidity was 55%, and the maintenance window was allocated for 90 minutes. The following details each step and its sub-steps.

[0186] Step S1: Base layer pretreatment

[0187] S1-1: High-pressure purging and brushing

[0188] A small high-pressure blower with a pressure of 0.8 MPa, used in conjunction with a stiff steel wire brush, is repeatedly blown and brushed along the longitudinal direction of the track to remove floating dust, loose debris, oil, and algae from the surface of the support layer. During operation, the blower nozzle is kept 10-15 cm away from the substrate, and the steel wire brush is applied with appropriate pressure to remove firmly attached contaminants. The purpose of this step is to eliminate the isolation layer, ensuring that subsequent materials can directly contact the solid substrate. If floating dust is not thoroughly removed, a weak interface layer will form between the powdering inhibitor and the substrate, reducing the bonding strength by more than 50%. High-pressure blowing is more effective than simple cleaning in removing fine particles from inside the pores, creating conditions for capillary penetration.

[0189] S1-2: Lightly sand to remove loose layers

[0190] For severely powdery areas (areas that appear powdery to the naked eye and leave noticeable scratches when lightly scratched with a key), a miniature angle grinder with an 80-grit diamond grinding disc is used for light grinding. The grinding depth is strictly controlled within the range of 3-5 mm until a uniform and hard concrete base surface is exposed. During operation, the grinder moves laterally back and forth along the track to avoid local depressions. Design basis: The powdery and deteriorated depth of the support layer is usually 2-5 mm. Grinding too shallowly (<2 mm) will not completely remove the loose layer, and the remaining powdery particles will hinder the penetration of inhibitors; grinding too deep (>5 mm) will unnecessarily remove healthy concrete and may touch the reinforcing steel protective layer. This step replaces the traditional chiseling process with "quantitative light grinding," which removes the deteriorated layer while preserving the integrity of the original structure to the greatest extent and avoiding disturbance to the geometric accuracy of the track.

[0191] S1-3: Leveling of localized spalling areas

[0192] For pitted areas with a depth ≥5 mm caused by powdering and peeling, after grinding, use the same TK-XB repair mortar as in step S3 (but adjust to a drier consistency with a powder-to-water ratio of 5:0.8) for pre-leveling to control the height difference of the base surface within ±2 mm. After applying the leveling layer, use a scraper to smooth it along the track direction and let it stand for 10 minutes to allow it to initially set. If leveling is not performed, the thickness of the repair mortar applied over a large area will be uneven, with insufficient strength in thin areas and shrinkage and cracking in thick areas.

[0193] S1-4: Moisture Content Testing and Environmental Verification

[0194] Using a portable concrete moisture meter (resistance type), five measuring points were randomly selected on the surface of the supporting layer to measure the moisture content within a 5 mm depth. The moisture content at all measuring points must be ≤10%. If the moisture content exceeds the standard, it should be dried using a hot air gun (temperature ≤60℃). Simultaneously, it was confirmed that the ambient temperature was within the range of -10℃ to 35℃, with no strong winds or rainfall. Design rationale: A moisture content ≤10% is a prerequisite for ensuring effective penetration and curing of the chalking inhibitor—excessive moisture dilutes the inhibitor, hinders capillary penetration, and reduces the bond strength between the epoxy system and the damp interface by approximately 40%. The curing reaction almost stops below -10℃, and curing is too rapid above 35℃, resulting in insufficient penetration depth.

[0195] Step S2: Apply TK-LVE-GDZC type chalking inhibitor

[0196] S2-1: Material Mixing

[0197] Measure the bottom inhibitor component (pre-packaged as two components A and B, where A is epoxy resin + silane coupling agent + nanofiller, and B is curing accelerator) according to the proportions in Example 1, and mix them at a mass ratio of A:B = 100:35. Stir at high speed (400-600 r / min) with a handheld electric stirrer for 3-5 minutes until the system is uniform and transparent. Let it stand for 1-2 minutes after stirring to defoam. The mixed material must be used within 30 minutes to prevent viscosity increase from affecting penetration. Design rationale: Insufficient stirring time will lead to uneven distribution of the curing agent, with some areas remaining uncured; excessive stirring time will introduce a large number of air bubbles, reducing the density after curing.

[0198] S2-2: Apply the first coat with a brush (to penetrate micro-cracks).

[0199] Using a 50 mm wide pig bristle brush, dipped in the mixed inhibitor, the material is first applied to the exposed microcracks (0.1-1 mm wide) after grinding, the corners around the sleepers, and the edges of the joints in the S1-3 leveling layer. The brush is used to "poke" the material into the depths of the cracks. The purpose of this step is to use the rigidity and tip of the brush to force the low-viscosity material into the tiny gaps that conventional rollers cannot reach. If this step is ignored, the air in the microcracks will hinder the subsequent roller application of material, causing these weak points to not be cured and becoming a source of recurrence.

[0200] S2-3: Apply a second coat using a roller in a cross-hatching pattern (topcoat coverage).

[0201] After the brush-coated area is surface dry (approximately 2-3 minutes), use a 4-inch fine-bristled roller (8 mm pile height) to apply inhibitor and roll it onto the tray to remove excess liquid. Then, apply the inhibitor to the entire area using a crisscross pattern: first apply one coat horizontally along the track, then one coat vertically, with an overlap of approximately 5 cm between each coat. When coating vertical surfaces (such as side walls), the roller should run at a 45° angle upwards to prevent material from flowing and forming tear marks. Design rationale: crisscrossing ensures complete coverage of the material on microscopically uneven surfaces, avoiding missed areas; the 45° angled application utilizes gravity to spread the material evenly on the side walls without dripping. The total usage should be controlled at 0.6-0.8 kg / m², monitored in real-time by weighing the material container before and after application.

[0202] S2-4: Precise dosage control

[0203] This step employs a "quantitative brushing method": The total required dosage is calculated in advance based on 0.7 kg / m². The mixed inhibitor is poured into a dedicated brushing tank with graduations. During brushing, after each 1 m² area is completed, the liquid level in the tank is checked to ensure it matches the theoretical dosage. If the dosage is less than 0.6 kg / m², the coating is too thin and needs to be reapplied; if it is greater than 0.8 kg / m², the material accumulates too thickly, resulting in waste and prolonged surface drying time. Design rationale: Dosage is directly related to penetration depth—0.6 kg / m² corresponds to approximately 3 mm penetration depth, and 0.8 kg / m² corresponds to approximately 4.5 mm. Below 0.6 kg / m², the penetration depth is less than 2 mm, failing to seal deep capillaries; above 0.8 kg / m², excess material forms a thick film on the surface, hindering oxygen participation in deep curing and increasing costs.

[0204] S2-5: Allow to dry completely.

[0205] After application, maintain good ventilation (but avoid strong winds) and allow it to stand for 15-20 minutes. The standard for determining surface dryness is: lightly touch the coating surface with your finger; it should feel non-sticky and show no material transfer. At this point, the inhibitor has lost its fluidity, but is still curing internally (complete curing requires 24 hours). This setting time has been optimized: less than 15 minutes will cause the trowel to damage the uncured inhibitor layer during surface mortar application, lifting it and causing poor mixing and adhesion; more than 20 minutes will result in over-curing of the inhibitor surface, reducing active groups and weakening the chemical bond with subsequent surface mortar. The 15-20 minute window allows the inhibitor to reach a "surface dry, internally moist" state, providing a stable substrate while retaining surface active groups for chemical anchoring.

[0206] Step S3: TK-XB Repair Mortar Surface Layer Construction

[0207] S3-1: Mortar Preparation

[0208] Take TK-XB dry powder (pre-packaged) according to the proportions in Example 1, add polymer emulsion and an appropriate amount of water, controlling the powder-to-water ratio within the range of 5:1 to 5:1.2 (i.e., add 1.0-1.2 kg of liquid per 5 kg of dry powder). Adjust the ratio according to the ambient temperature: 5:1.1 at 15℃. Stir with a handheld electric mixer at low speed (300 r / min) for 5 minutes until uniform, lump-free, and paste-like with good flowability (consistency approximately 80-100 mm, according to JGJ / T 70 slack-table flowability method). Let stand for 2 minutes after stirring to defoam. The material must be used within 30 minutes. Design rationale: A powder-to-water ratio that is too low (above 5:1.3) results in an overly thin mortar, causing dripping during application, difficulty in controlling thickness, and reduced strength; a powder-to-water ratio that is too high (below 5:0.9) results in an overly dry mortar, poor adhesion to the substrate, and difficulty in compaction. This proportion has been optimized through testing, providing optimal workability while ensuring a 2-hour strength ≥15 MPa.

[0209] S3-2: First thin coating (interface transition layer)

[0210] Using a stainless steel trowel (15 cm wide), apply a small amount of mortar evenly to the surface-dried inhibitor layer, controlling the thickness to 1-2 mm. Hold the trowel at a 30° angle to the substrate and press firmly to ensure the mortar is fully embedded in the microscopic rough structure of the inhibitor surface. This layer, called the "interfacial transition layer," serves to establish both chemical and mechanical anchoring: on one hand, the polymer emulsion in the mortar cross-links with the active epoxy groups on the inhibitor surface; on the other hand, the thin mortar layer fills the tiny irregularities on the inhibitor surface under pressure, forming an interlocking structure. If this layer thickness exceeds 2 mm, the internal shrinkage stress of the transition layer increases, which reduces the bond strength; if it is less than 1 mm, continuous coverage cannot be formed, and localized debonding is likely to occur.

[0211] S3-3: Apply the second coat to the designed thickness.

[0212] Apply the second coat within 8-12 minutes after the first coat (before initial setting, which typically takes about 20-25 minutes). Use the same trowel for the second coat, thickening the mortar to the total designed thickness (adjusted within 3-8 mm depending on the degree of damage). For slightly chalking areas (surface wear <2 mm), the total thickness should be 3 mm; for moderate chalking (peeling depth 2-5 mm), the total thickness should be 5-6 mm; for severe peeling (depth 5-8 mm), the total thickness should be 8 mm. Smooth the mortar along the longitudinal direction of the track, using a trowel at a 60° angle in one stroke to avoid repeated troweling that could cause surface bleeding. Design rationale: Layered application (thin layer + thick layer) is more effective at removing air bubbles and reducing shrinkage cracks than a single thick coat. The interval between the two coats should be controlled before initial setting to ensure complete fusion between the layers, preventing segregation.

[0213] S3-4: Surface leveling and joint treatment

[0214] Use a long ruler (1.5 m long aluminum alloy scraper) to smooth the surface longitudinally along the track, making the repair mortar surface flush with the original supporting layer surface, with a height difference not exceeding ±1 mm. At the joint with the existing concrete, use the tip of a trowel to press out a micro-V-shaped groove 2-3 mm wide (1 mm deep) along the joint. This is to release shrinkage stress and prevent cracking at the joint. After smoothing, let it stand without further finishing to maintain the rough texture and improve adhesion to any subsequent protective layer.

[0215] S3-5: Time Window Control

[0216] The entire S3 step (from mixing to smoothing the second layer) must be completed within 20 minutes, ensuring all operations are finished before the mortar initially sets. A timer is used for strict control on-site. Design basis: The initial setting time of this mortar is 25-30 minutes (adjusted by a retarder). If troweling continues beyond the initial setting time, the already formed hydration product network will be damaged, resulting in a strength reduction of more than 30%. Completing within 20 minutes allows for some leeway to ensure construction quality.

[0217] Step S4: Node-specific reinforcement

[0218] S4-1: Identification of Stress Concentration Regions

[0219] Using a steel ruler and marker, mark the reinforced areas on both sides of the longitudinal joint where the support layer meets the base plate, and within a 10 cm width directly below each sleeper. These areas bear the maximum shear force and bending moment of the train's dynamic load and are the most prone to recurrence of pulverization and spalling. Design basis: Finite element analysis shows that the peak shear stress of the support layer below the sleeper edge is 2.5 times that of other areas; due to the abrupt change in stiffness at the joint, the tensile stress concentration factor is as high as 3.0. Ordinary uniform construction is insufficient to meet the durability requirements of these joints.

[0220] S4-2: Apply double the base coat

[0221] A bottom-layer reinforcement coating process is applied to the node area. This reinforcement coating is performed in step S2, increasing the dosage by an additional 0.1 kg / m² on top of the original total chalking inhibitor dosage (0.6-0.8 kg / m²), bringing the total dosage for the node area to 0.7-0.9 kg / m². During application, a brush is used to apply the inhibitor, covering a 5 cm wide area on both sides of the node, and then brushing once perpendicular to the joint direction. Design rationale: Due to stress concentration, the density of microcracks in the concrete at the node area is 2-3 times that of ordinary areas, requiring more inhibitor penetration and filling. Doubling the dosage (0.1 kg / m²) allows the penetration depth in this area to reach more than 5 mm, forming a super-strong consolidation zone.

[0222] S4-3: Thickened surface mortar

[0223] In step S3, the total thickness of the repair mortar in the joint area is increased to 8-10 mm (2-4 mm thicker than in ordinary areas). During construction, after applying the second layer and before smoothing, an additional thin layer of mortar is added and compacted, making this area slightly higher than the surrounding surface (approximately 0.5 mm). After hardening, it is ground smooth with an angle grinder. Design rationale: The thicker layer provides a larger load-bearing cross-sectional area, reducing the average stress at the joint; at the same time, a thicker mortar layer can better absorb and disperse vibration energy. If the thickness is less than 8 mm, the reinforcement effect is insufficient; if it exceeds 10 mm, it may interfere with the fit clearance between the sleeper and the support layer.

[0224] S4-4: Compact and seal along the seam

[0225] Using the tip of a trowel, repeatedly press the mortar at the joint area into the gaps, ensuring the mortar fully fills the gaps (the gap width is typically 1-3 mm), with a filling depth of ≥5 mm. Then smooth the surface, ensuring the mortar adheres tightly to the substrate on both sides. This operation is similar to "caulking and sealing," aiming to completely block the path of moisture seepage along the joint. Without compaction and sealing, even if the surface coating is complete, water can still penetrate the underlying substrate along the sides of the joint, causing the defects to recur from the edges inward. Actual tests show that joints sealed with compaction and sealing showed no leakage during water spray tests, while the unsealed control group showed signs of water seepage after 30 minutes.

[0226] Step S5: Effectiveness Verification (Non-destructive Quality Control Closed Loop)

[0227] S5-1: Immediate visual inspection and percussion test

[0228] Within 5 minutes of completion, conduct an immediate inspection: Visually inspect the inhibitor coating for any missed areas, accumulation, or dripping; ensure the mortar surface is smooth, without cracks or whitening; gently tap the mortar surface with a small rubber hammer; the sound should be crisp and solid, without any hollow "thump" sounds. If hollow areas are found, immediately grooving the edge of the hollow area and injecting diluted inhibitor to remedy the situation. Design rationale: Immediate inspection allows for timely correction of obvious defects within the grace period, preventing lingering problems from affecting operations. Hollow areas are usually caused by uncleaned base layer dust or trapped air bubbles during application; the tapping method is the fastest and most effective detection method.

[0229] S5-2: Retest of compressive strength after 2 hours (before the end of the window period)

[0230] Two hours after construction (approximately 10 minutes before the end of the maintenance window), a handheld rebound hammer (correlation coefficient R² ≥ 0.98) calibrated against the 28-day compressive strength of a standard test block with the same mix proportion was used. Ten rebounds were performed at each of the three test points in the non-node area, and the average rebound value was calculated and converted to compressive strength according to the calibration curve. The converted strength was required to be ≥ 15.0 MPa. If on-site calibration was not possible, pre-prepared test blocks cured under the same conditions (40mm × 40mm × 160mm) could be used for compressive strength testing, with a required measured strength ≥ 15.0 MPa. A simple adhesion test was also conducted: tape was adhered to the mortar surface, and after a strong pull, no powdery particles fell off the tape. Design basis: The 2-hour strength is a crucial indicator for determining whether traffic can be resumed. This method utilizes the rapid hardening characteristics of the surface mortar; the measured 2-hour strength can reach over 16.2 MPa, far exceeding the safety threshold. If the rebound value is too low (e.g., <13 MPa), the window time needs to be extended or temporary support needs to be provided, but this situation has never occurred in this embodiment.

[0231] S5-3: Mid-term follow-up examination in 7 days

[0232] Seven days after construction, a non-metallic ultrasonic testing instrument was used to measure the wave velocity in the repaired area and compare it with that of the healthy area. A wave velocity ratio ≥ 0.95 (reflecting density) was required. Simultaneously, a 5x magnifying glass was used to inspect the surface for micro-cracks. Design basis: After 7 days, the mortar strength reached over 40 MPa, and shrinkage was essentially complete. Ultrasonic wave velocity can non-destructively assess internal density and bond integrity. A wave velocity ratio < 0.9 indicates internal debonding or honeycombing.

[0233] S5-4: Final inspection after 28 days

[0234] Twenty-eight days after construction, the following non-destructive / micro-destructive tests were conducted: ① Drilling Φ20 mm core samples (one per 100 m², filled with epoxy resin) to test the compressive strength (≥55 MPa) and bond interface shear strength (≥2.5 MPa with cohesive failure); ② Observing the side of the core sample using a penetration depth tester (miniature endoscope) to measure the inhibitor penetration depth (≥3 mm); ③ Conducting on-site rapid chloride ion testing (using the chloride ion selective electrode method), requiring the surface chloride ion content to be lower than 50% of the unrepaired control area. All test data were recorded and archived, forming a "quality control ID card" for each repair site. Design basis: The 28-day final inspection fully verified the long-term performance of the two-layer system. In this embodiment, the measured 28-day compressive strength was 62.8 MPa, penetration depth was 4.0 mm, bond strength was 3.3 MPa (cohesive failure), and the chloride ion diffusion coefficient was 0.82 times that of the original concrete, all of which were qualified.

[0235] The total construction time is compatible with the skylight period.

[0236] The total time taken in this embodiment, from the start of base layer pretreatment to the completion of S5-1 immediate inspection, is summarized as follows:

[0237] S1 (Pretreatment): 18 minutes (S1-1: 5 minutes, S1-2: 8 minutes, S1-3: 3 minutes, S1-4: 2 minutes)

[0238] S2 (Apply inhibitor): 12 minutes (S2-1: 3 minutes, S2-2: 3 minutes, S2-3: 4 minutes, S2-5: 20 minutes resting, running concurrently with subsequent steps, not included in the main time)

[0239] S3 (mortar construction): 22 minutes (S3-1: 4 minutes, S3-2: 5 minutes, S3-3: 8 minutes, S3-4: 3 minutes, S3-5: 2 minutes)

[0240] S4 (Node Reinforcement): 8 minutes (runs in parallel with S3, actual time increase is negligible)

[0241] S5-1 (Immediate Inspection): 5 minutes

[0242] The total time taken for the main line is 18 + 12 + 22 + 5 = 57 minutes. Adding the 20-minute settling time for S2-5 (during which other preparatory work, such as mortar preparation, can be carried out), the actual time occupied during the maintenance window is approximately 77 minutes, less than 90 minutes. This fully meets the requirements of a standard maintenance window for high-speed rail. Even in the event of a shorter maintenance window (e.g., 90 minutes), there is still room for adjustment.

[0243] Summary of technical features in this embodiment

[0244] 1. Quantitative grinding depth (3-5 mm): Unlike the traditional "experience-based chiseling", this invention determines the typical depth range of the powdery and deteriorated layer through experiments, and adopts light grinding instead of destructive chiseling, which removes the deteriorated layer while preserving the original structure to the maximum extent and avoids disturbance to the track geometry accuracy.

[0245] 2. Brush + Roller Co-coating Process: This innovative two-step method, combining brush application to cracks with roller cross-covering, solves the industry problem of a single roller being unable to fill micro-cracks. The forced application of the brush allows for a crack filling depth of over 5 mm, far exceeding the 2 mm achieved with rollers alone.

[0246] 3. Precise control of the 15-20 minute settling window: Through extensive experimentation, a surface drying time window was determined that ensures the substrate loses its fluidity to provide a stable base while preserving surface-active groups for chemical bonding with the surface layer. The discovery of this window is one of the key innovations of this invention.

[0247] 4. Coordinated application of layers: The second layer should be applied within 8-12 minutes after the first thin coat (before initial setting) to ensure that the two layers are fused together and avoid delamination between layers caused by excessive time intervals in conventional construction.

[0248] 5. Three-pronged approach to joint reinforcement: Doubling the amount of inhibitor, thickening the mortar, and compacting and sealing the joints are used to strengthen the joints in areas of stress concentration. This creates localized super protection and solves the problem of easy recurrence of joints in existing technologies.

[0249] 6. Four-stage non-destructive quality control closed loop: Establish a full-cycle testing system of "instantaneous - 2h - 7d - 28d", adopting non-destructive or minimal-destructive methods throughout, forming traceable quality control data for each work site, and completely changing the traditional extensive mode of "relying on experience and without records".

[0250] Comparison and verification

[0251] The precise construction method of this embodiment is compared with that of the comparative example (method of patent CN202211358568.1) in the same pulverization section:

[0252]

[0253] The results show that this embodiment is significantly superior to the existing technology in terms of repair depth, early strength, construction efficiency, and durability.

[0254] In summary, this invention, through material innovation in a dual-layer repair system and process control of precise construction methods, achieves the synergistic goals of inhibiting pulverization and improving durability of the ballastless track support layer. It improves the maintenance and repair technology system for the ballastless track support layer of high-speed railways, ensures the long-term safe operation of the line, and reduces the total life-cycle maintenance cost, demonstrating significant economic and social benefits.

[0255] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A two-layer synergistic repair system for ballastless track support layers, characterized in that, include: The bottom layer is a low-viscosity reactive powdering inhibitor that can penetrate into the capillary pores of the support layer and solidify in situ, used to seal deep moisture and ion intrusion channels and solidify the loose layer. The surface layer is a fast-hardening, low-shrinkage, high-adhesion polymer repair mortar that covers the bottom layer to form a dense protective layer that resists traffic loads and environmental erosion. The bottom layer and the surface layer are chemically compatible and form an integrated synergistic structure of "deep consolidation-surface protection" through interfacial chemical bonding to block the vicious cycle of "pulverization-water intrusion".

2. The dual-layer synergistic repair system according to claim 1, characterized in that, The powdering inhibitor is a reactive composite system with a viscosity of ≤10 mPa·s at 25℃, a penetration depth of ≥3 mm, and a bond strength with concrete of ≥3.0 MPa, exhibiting cohesive failure within the substrate. The repair mortar is a polymer-modified cement-based composite material with a 2-hour compressive strength of ≥15.0 MPa, a 28-day shrinkage rate of ≤0.10%, and a 28-day bond strength of ≥2.5 MPa, exhibiting cohesive failure within the concrete.

3. The dual-layer synergistic repair system according to claim 1 or 2, characterized in that, The chalking inhibitor is composed of low-viscosity epoxy resin, silane coupling agent, nano-reinforcing filler, and composite curing accelerator, and by weight, it contains: 100 parts of bisphenol A type epoxy resin, 5-15 parts of γ-aminopropyltriethoxysilane, 2-10 parts of nano-silica, and 30-40 parts of modified aliphatic amine curing agent; the repair mortar is composed of polymer emulsion, high-strength silicate cement, graded quartz sand, composite expansion agent, retarder and accelerator, and water-retaining agent, and by weight, it contains: 120-180 parts of acrylate copolymer emulsion, 350-450 parts of P·II52.5 grade silicate cement, 400-500 parts of graded quartz sand, 20-40 parts of U-type expansion agent, 3-8 parts of retarder and accelerator compounded with tartaric acid and sodium sulfate in a 1:4 ratio, and 0.5-2 parts of hydroxypropyl methylcellulose.

4. A precise construction method for suppressing pulverization and improving durability of ballastless track support layers using the dual-layer synergistic repair system described in any one of claims 1-3, characterized in that, Includes the following steps: Base treatment: Clean and lightly grind the surface of the supporting layer to remove loose layers; Penetration reinforcement: Apply the chalking inhibitor, controlling its dosage and penetration depth, and let it stand until surface dry; Surface repair: Apply the repair mortar in layers, controlling its thickness and construction time, to form a repair layer; Node reinforcement: For stress concentration areas in the support layer, increase the amount of the powdering inhibitor and / or increase the thickness of the repair mortar and compact and seal it; Performance verification: At predetermined time points after construction, the key performance indicators of the repair layer are tested using non-destructive or minimal-destructive methods to form a quality control closed loop; The construction method described herein has a total operation time of ≤90 minutes per work site, which is suitable for the high-speed rail operation window period.

5. The method according to claim 4, characterized in that, The underlying processing further includes: S1-1: Use a high-pressure blower with a pressure ≥0.8MPa and a wire brush to remove floating dust, loose debris and oil stains from the surface of the support layer; S1-2: Lightly grind the severely pulverized areas using a micro angle grinder, with a grinding depth of ≤5mm, to remove the loose surface layer and expose the solid base surface; S1-3: Level the base surface for areas with localized peeling depth ≥5mm; S1-4: Test the moisture content of the base layer to ensure that the moisture content within 5mm of the surface layer is ≤10%, and the construction environment meets the requirements of temperature -10℃~35℃ and no strong winds or rainfall.

6. The method according to claim 4, characterized in that, The penetration reinforcement further includes: S2-1: Mix the powdering inhibitor according to the product instructions, and stir at high speed with a hand-held electric mixer for 3-5 minutes until uniform; S2-2: Use a combination of brush and roller for application. First, apply one coat evenly with a brush to ensure that the material penetrates into micro-cracks and pores. S2-3: Apply another coat using a roller in a crisscross pattern, using a 45° angled brushing path when painting vertical surfaces; S2-4: Control the total dosage of powdering inhibitor within the range of 0.6-0.8 kg / m²; S2-5: After application, let stand for 15-20 minutes until the material is surface dry before proceeding with subsequent construction.

7. The method according to claim 4, characterized in that, The surface repair further includes: S3-1: Add water to the repair mortar at a powder-to-water ratio of 5:1 to 5:1.2, and stir with a hand-held electric mixer for 5 minutes until it is uniform, free of lumps, and has suitable fluidity; S3-2: Apply the coating in layers using a trowel. The first thin layer serves as an interface transition layer, with a thickness controlled within the range of 1-2mm, to ensure full adhesion with the underlying chalking inhibitor. S3-3: Before the first layer sets, apply the second layer to the designed thickness within 1 hour. The total thickness should be adjusted to 3-8mm depending on the degree of surface damage. For the node areas identified in step S4-1, the total thickness of the repair mortar should be increased to 8-10mm in this step. S3-4: When applying, scrape along the longitudinal direction of the track to ensure that the surface is flat and flush with the original support layer surface, with no obvious seams; S3-5: The mixed repair mortar should be used within 30 minutes, and the second layer should be applied before initial setting.

8. The method according to claim 6, characterized in that, The node reinforcement further includes: S4-1: Identify and locate the stress concentration area at the junction of the support layer and the base plate, and under the sleeper; S4-2: Implement a bottom-layer reinforcement coating process in the node area. This reinforcement coating is performed in step S2, with an additional 0.1 kg / m² of coating on top of the original total amount of inhibitor. When coating, cover an area 5 cm wide on both sides of the node. S4-3: Implement a surface thickening process in the node area. This thickening process is performed in step S3-3, increasing the thickness of the repair mortar to 8-10mm. S4-4: After leveling in step S3-4, compact and seal the repair mortar along the joint direction to ensure that the gap is fully filled and there are no hollow areas.

9. The method according to claim 4, characterized in that, The effect verification further includes: S5-1: Immediately after construction is completed, conduct visual and tapping inspections to check for any missed coatings, material accumulation, drips, or hollow areas. S5-2: A re-inspection should be conducted 2 hours after construction to check whether the compressive strength of the repair mortar reaches ≥15.0MPa; S5-3: A re-inspection shall be conducted 7 days after construction to test the 7-day compressive strength of the repair mortar ≥40.0MPa, the 7-day flexural strength ≥8.0MPa, and the bonding performance. S5-4: A re-inspection shall be conducted 28 days after construction to test the penetration depth of the chalking inhibitor, the 28-day compressive strength of the repair mortar (≥55.0MPa), the 28-day flexural strength (≥12.0MPa), the 28-day bond strength, the 28-day shrinkage rate (≤0.10%), the alkali resistance, and the relative dynamic modulus of elasticity after 300 freeze-thaw cycles (≥60%) with a mass loss rate (≤5%). Step S5 forms a non-destructive quality control closed loop.

10. The application of the dual-layer synergistic repair system according to any one of claims 1-3 in the treatment of pulverization and / or spalling defects in the support layer of ballastless track.

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