A method and material for repairing ballastless track bed plate pulverization suppression

Abstract

A special material and method for inhibiting and repairing pulverization of ballastless track slabs. The special material is a low-viscosity reactive organic-inorganic hybrid pulverization inhibitor, comprising epoxy resin, reactive diluent, silane coupling agent, nano-silica, and composite curing accelerator. Its viscosity at 25℃ is ≤10 mPa·s, allowing it to penetrate ≥3 mm into the concrete, generating a three-dimensional silica-oxygen network in situ. This chemically bonds and strengthens the loose matrix, achieving an interfacial tensile bond strength ≥3.0 MPa and increasing cohesion by ≥150%. The repair method includes local cleaning, inhibitor application and penetration, filling defects with quick-setting mortar, and setting regular transverse joints to release temperature stress. The total construction time is ≤2 hours, suitable for railway track maintenance windows. This invention utilizes a synergistic "penetration and strengthening - mortar repair - regular jointing" approach, resulting in a ≥20% increase in rebound strength after repair, ≥300 freeze-thaw cycles, and a reduction in chloride ion diffusion coefficient to 1 / 5-1 / 10 of the original concrete, effectively inhibiting pulverization recurrence and preventing cracking of the repair layer.

Description

Technical Field

[0001] This invention relates to a repair method and materials, and more particularly to a method and materials for inhibiting the pulverization of ballastless track slabs. Background Technology

[0002] Ballastless track, as a core technology of high-speed railway track systems, has become the mainstream choice for high-speed rail construction worldwide due to its significant advantages such as high smoothness, high stability, and low maintenance. It is widely used in key national lines such as the Beijing-Shanghai High-Speed ​​Railway, the Harbin-Dalian High-Speed ​​Railway, and the Shanghai-Hangzhou High-Speed ​​Railway. The track slab, as a key load-bearing structure of ballastless track, directly bears the dynamic load transmitted by high-speed trains and is exposed to the complex outdoor service environment for extended periods, serving as the "lifeline" for ensuring the safe operation of the line. Its design life is typically required to be no less than 60 years. However, in actual service, due to the combined effects of multiple severe factors, a large amount of track slab concrete with a strength below 40MPa prematurely exhibits powdering and spalling defects, seriously threatening the safety and economy of high-speed rail operation, becoming a core technical problem that the industry urgently needs to solve.

[0003] Currently, the pulverization and spalling of ballastless track slabs has become widespread, severe, and rapidly developing. According to a field survey of 12 key high-speed railway lines across the country (covering different climate regions such as cold regions, coastal areas, and subtropical areas), the incidence rate of the disease is as high as 38%, and it is concentrated on lines that have been in service for 10-15 years. Based on the severity of deterioration, it can be clearly divided into three levels: Slight pulverization is characterized by surface sanding and sludge peeling, resulting in loose concrete surface slurry, loss of water tightness, and the formation of a network of microcracks. At this stage, the surface impermeability and strength begin to decline, providing channels for the continuous intrusion of moisture and harmful ions, accelerating the risk of internal steel reinforcement corrosion. This stage accounts for approximately 52% of all lines. Moderate pulverization is characterized by surface peeling, spalling, and exposed aggregate, with separation of aggregate and slurry. The elastic modulus of the concrete is lower than 80% of the design value, the average pulverization depth in the affected area is ≤2cm, and the compressive strength of the concrete below the pulverized layer is not lower than 70% of the original strength, accounting for approximately 35%. Severe pulverization is characterized by large-area spalling, defects, and exposed reinforcement, with exposed and corroded reinforcement in localized areas. The structural integrity is severely damaged, the average spalling depth of the concrete is >2cm, and the compressive strength of the concrete below the pulverized layer is lower than 70% of the original strength, with some areas even showing zero strength, accounting for approximately 13%. It is worth noting that the disease exhibits a development pattern of "from the surface to the interior, from minor to severe". It only takes 3-5 years for the disease to progress from slight sanding to severe exposed rebar. Moreover, the degree of pulverization increases significantly after each winter, forming a vicious cycle of "deterioration-water accumulation-more severe deterioration".

[0004] From both a technological and market perspective, the industry's demand for ballastless track slab pulverization repair is now urgent. Technologically, existing repair solutions generally suffer from poor adaptability, incomplete repair, and low construction efficiency. There is a lack of specialized inhibitory materials for track slabs with a strength below 40MPa, making it impossible to achieve deep penetration and consolidation to block the root cause of deterioration, and also difficult to adapt to the rapid construction requirements during track maintenance windows. Market-wise, my country's high-speed rail operating mileage has exceeded 45,000 kilometers, with many early-built lines entering a period of high incidence of track defects. The annual expenditure on track slab maintenance exceeds 10 billion yuan. Traditional repair methods are not only costly and time-consuming but also frequently disrupt normal operations. The market urgently needs new repair technologies that are economical, efficient, and have minimal impact on operations. The research and application of such technologies not only meet the national strategic requirements for high-speed rail safety operation and maintenance but also provide key support for the industry to reduce maintenance costs and improve operational efficiency, possessing significant technological value and market application prospects.

[0005] In response to the aforementioned characteristics of the defects and the difficulties in their repair, there is an urgent need to develop a specialized technology that can deeply strengthen the loose matrix, prevent cracking of the repair layer, and adapt to the special service environment of the track bed slab and the requirements for rapid construction during maintenance windows. In particular, the treatment of joints in the repair area, by setting induced joints to control the direction and location of cracks, concentrates shrinkage deformation within pre-designed structural joints, and avoids irregular cracks in the repair layer that could affect structural performance.

[0006] Currently, the repair solutions for pulverized track slabs of ballastless tracks are mainly divided into three categories, and none of them have formed a dedicated technical system adapted to the pulverization characteristics of track slabs:

[0007] The first type is polymer-modified cement mortar surface sealing technology. This involves using ordinary polymer emulsion-modified cement mortar to cover the powdery areas, relying on cement hydration and polymer film formation to form a sealing layer. This type of material has high viscosity and coarse particle size (typically >100μm), making it difficult to penetrate the loose pores inside the track slab (pore size mostly <50μm). It only forms a physical covering layer on the surface and cannot fill internal micro-cracks. Furthermore, cement-based materials have a high shrinkage rate (typically >0.05%) and low interfacial bond strength with old concrete (<1.5MPa), making them prone to delamination and detachment under temperature deformation of the track slab and train vibration. In addition, ordinary cement-based materials have a long curing period (>7 days), which is incompatible with the rapid construction requirements during railway maintenance windows. They are prone to secondary cracking and detachment due to shrinkage differences, making them unsuitable for rapid construction during maintenance windows.

[0008] The second type is grouting reinforcement and repair technology, which targets defects such as pulverization accompanied by cracks. It employs a combination of side-crack sealing and drilling grouting, injecting fast-hardening polymer grout to fill the gaps and bond the track bed slab to the base. However, this technology is cumbersome (requiring multiple steps such as cleaning, drilling, grouting, and sealing), has stringent requirements for grouting pressure control, makes it difficult for large equipment to operate in the track area, and the grout's limited permeability cannot cover large areas of loose, pulverized material, resulting in high remediation costs and low efficiency. More importantly, grouting only solves crack problems; it lacks effective treatment for large-area surface pulverization defects and does not consider post-repair joint treatment, making it impossible to prevent subsequent cracking due to temperature stress.

[0009] The third type is silane impregnation surface protection technology. This involves using traditional silane impregnating agents, sprayed or rolled onto slightly chalking surfaces, forming a hydrophobic layer to block moisture penetration. However, this technology only works on the concrete surface, with a penetration depth typically less than 1mm. It cannot fill internal capillary pores and micro-cracks, and therefore cannot strengthen the loose matrix at its source. Furthermore, before application, the substrate moisture content must be ≤8% and the surface strength ≥25MPa. It has poor compatibility with severely chalking, low-strength track slabs, and its protective effect is rapidly diminished by freeze-thaw cycles and ultraviolet radiation, with a durability of less than 5 years. Additionally, silane impregnation is a surface protection method and does not address structural defects or joint control, failing to solve the shrinkage cracking problem during large-area repairs.

[0010] Based on the currently disclosed patent portfolio, existing patent technologies also have obvious shortcomings in scenario adaptability, and cannot completely solve the core pain point of track bed slab pulverization repair:

[0011] Patent CN104987027B discloses a repair material for cracks in concrete track slabs of high-speed railway ballastless tracks. It uses nano-silica sol as its core component, achieving micro-crack sealing by stimulating unhydrated cement particles within the concrete. However, this technology only addresses single crack repair and cannot handle large-area powdering defects. Furthermore, the strength increase of the repaired track slab is only 4.5%-9.1%, far below the matrix strengthening requirements for low-strength track slabs below 40MPa. Additionally, this patent does not address joint control technology, failing to prevent shrinkage and temperature-induced cracking in large-area repair layers.

[0012] Patent CN211645779U discloses a durable and flexible structure for a waterproof sealing layer of high-speed railway subgrade, employing a multi-layer protection system of "flexible treatment layer + elastic isolation layer + asphalt sand waterproof layer". However, its construction process is cumbersome, material costs are high, and the overall construction cycle is long, making it completely unsuitable for the rapid construction requirements during railway maintenance windows. Furthermore, this technology is only designed for the waterproof sealing layer of the subgrade and cannot penetrate and consolidate the loose matrix of the track bed slab to strengthen it, thus failing to block the path of pulverization and deterioration at its source.

[0013] Patent CN106320114A discloses a method for repairing concrete damage to high-speed railway base plates, which involves applying an interface agent followed by filling with repair mortar to repair surface defects. However, the interface agent in this technology can only act on the surface and cannot penetrate to strengthen the loose matrix beneath the powdery layer, thus failing to achieve deep consolidation. Furthermore, its joint design simply retains the original structural expansion joints without considering the shrinkage and temperature deformation of the repair layer itself, leaving the repair layer at risk of irregular cracking.

[0014] Patent CN202211358568 proposes a unitized treatment method for pulverization defects in the support layer of high-speed railways, enabling construction during maintenance windows through small unit division. However, this technology targets the low-strength C15 support layer, which differs significantly from the high-load-bearing, high-frequency vibration service environment of the track slab; the non-film-forming anti-stripping agent it uses has limited penetration depth, failing to achieve the 3mm or deeper penetration and consolidation of this invention; furthermore, its joint design is not optimized to adapt to the deformation characteristics of the repair layer, failing to fully release the stress in the repair layer.

[0015] The core ideas of the above solutions all revolve around "covering" or "partial filling," without fully considering the root causes of pulverization and deterioration of ballastless track slabs (especially loose substrates with a strength below 40MPa), the coupling effect of train dynamic loads and environmental erosion, and the strict limitations of rapid construction during railway maintenance windows. In particular, they neglect the temperature deformation characteristics and joint control requirements of track slabs as narrow and thin-walled structures, resulting in shrinkage cracks and interface peeling after repair, and insufficient technical relevance and scenario adaptability.

[0016] The aforementioned prior art has the following drawbacks:

[0017] (1) Mismatch between material permeability and consolidation capacity: Existing repair materials are either too viscous to penetrate into the interior (such as polymer mortar) or can only adhere to the surface and cannot strengthen the matrix (such as silane), neither of which can form an effective consolidation structure in the interior of low-strength loose concrete; at the same time, cement-based materials have large shrinkage and weak adhesion, and are prone to peeling at the interface with concrete below 40MPa, and cannot uniformly fill the internal pore network, and the adhesion at the interface with the original concrete is prone to failure, and cannot form a synergistic stress system.

[0018] (2) Insufficient construction efficiency and adaptability to track maintenance window: Traditional technical procedures are complicated (such as polymer mortar repair, which requires multiple steps of "cleaning-anchoring-filling-curing"), and the curing cycle is as long as 3-7 days, far exceeding the time limit of railway track maintenance window (90-240 minutes); grouting reinforcement requires large equipment, the working space in the track area is limited, and a single repair requires 1-2 track maintenance windows; silane impregnation has strict requirements on the dryness of the base surface (moisture content ≤8%), and the pretreatment takes a long time, which further reduces construction efficiency and seriously interferes with railway operation and scheduling.

[0019] (3) Insufficient repair depth and root cause treatment: Existing technologies mostly focus on "surface covering" or "partial sealing". The penetration depth of silane impregnation is less than 1 mm, and the cement-based sealing coating is only attached to the surface. Neither can penetrate deep into the capillary pores and micro-cracks inside the track bed slab. Grouting reinforcement can only treat cracks in a targeted manner and is difficult to cover large areas of powdery areas. It cannot strengthen the density of the loose matrix from the root, resulting in repeated recurrence of powdery diseases and forming a vicious cycle of "repair-deterioration-re-repair".

[0020] (4) Poor interfacial bonding and structural synergy: The bonding strength between cement-based sealing coating and powdery substrate is usually <1.5MPa. Affected by train vibration (frequency 5-20Hz) and temperature changes, it is prone to hollowing, peeling and falling off; the layered structure formed by polymer mortar repair has poor coordination with the deformation of the original concrete, and the interface is prone to peeling. It cannot withstand dynamic loads together, and new cracking and powdering are likely to occur at the interface in the later stage. Especially when large-area continuous pouring repair is carried out, since no joints are set, temperature stress and shrinkage deformation have nowhere to be released, which will inevitably lead to cracking of the repair layer.

[0021] (5) Lack of joint control and crack prevention: Existing repair techniques all adopt large-area continuous pouring or continuous coating methods, without considering the expansion and contraction characteristics of the narrow and thin-walled structure of the track bed under the influence of solar temperature difference and seasonal temperature changes. During the hardening process, the repair layer undergoes volume shrinkage and is simultaneously constrained by the base layer to generate tensile stress. When the tensile stress exceeds the tensile strength of the material, cracks will occur. In contrast, under the action of temperature cycling, the location of cracks in the continuous and seamless repair layer is random and uncontrollable. It is very easy for through cracks to occur at stress concentration points (such as around fasteners or the original crack location), leading to moisture intrusion and recurrence of the disease, which seriously affects the repair life. Summary of the Invention

[0022] To address the shortcomings of existing technologies, this invention discloses a special material for inhibiting and repairing pulverization of ballastless track slabs. The technical solution is as follows: A special material for inhibiting and repairing pulverization of ballastless track slabs, characterized in that the special material is a low-viscosity, high-permeability, reactive organic-inorganic hybrid pulverization inhibitor. Its viscosity at 25°C is ≤10 mPa·s, and it can spontaneously penetrate into the interior of track slab concrete with a strength grade below 40 MPa, with a penetration depth ≥3 mm. It also generates a three-dimensional silicon-oxygen network structure in situ, forming chemical bonds with concrete hydration products to achieve integrated "penetration-filling-consolidation-reinforcement".

[0023] The special material comprises component A and component B by volume ratio, wherein the mixing ratio of component A to component B is 4:1, wherein:

[0024] The A component comprises: 38-45 parts by weight of low viscosity epoxy resin, 12-18 parts by weight of reactive diluent, 2-4 parts by weight of silane coupling agent, and 1-3 parts by weight of nano-reinforcing filler.

[0025] Component B comprises: 2-3 parts by weight of a composite curing accelerator;

[0026] After curing, the special material has a tensile bond strength of ≥3.0MPa with concrete with a strength grade of 40MPa or below, and increases the cohesion of the repaired track slab concrete by ≥150%, has a freeze-thaw cycle resistance of ≥300 times, and reduces the chloride ion diffusion coefficient to 1 / 5 to 1 / 10 of the original concrete.

[0027] This invention also discloses a method for inhibiting and repairing pulverization of ballastless track slabs using the aforementioned special materials, characterized in that the method includes the following steps:

[0028] Step 1: Base cleaning

[0029] For areas of pulverized track slabs, locally remove loose surface layers with a thickness ≤5mm, retaining a solid base layer; use a high-pressure blower to clean away dust, debris, and oil stains, ensuring the base layer is dry, clean, free of loose particles and standing water, with a moisture content ≤10%;

[0030] Step 2: Apply chalking inhibitor

[0031] After mixing component A and component B of the special material evenly at a volume ratio of 4:1, apply the mixture 2-3 times with a short-nap roller on the cleaned base layer in a crisscross pattern, with an interval of 10-15 minutes between each application. The application rate is 0.4-0.6 kg / m². Continue until the adhesive stops seeping and the base surface shows a continuous wet gloss, forming a fully penetrated standard, allowing the inhibitor to penetrate the base layer ≥3 mm.

[0032] Step 3: Repairing Cracks and Damage

[0033] After the inhibitor applied in step 2 has dried to the touch, the cracks and damaged areas on the track bed slab should be graded and treated accordingly:

[0034] For fine cracks with a width of <1.0mm, they can be filled by the already penetrated and cured inhibitor without any additional treatment;

[0035] For wide cracks ≥1.0mm and obvious defects, use quick-hardening repair mortar to fill and compact them, apply in layers, each layer ≤10mm thick, and ensure that the surface is flush with the original track bed slab.

[0036] For exposed rusted steel bars, first use a wire brush to remove the rust, then apply an anti-rust primer, and after the primer is surface dry, wrap and cover it with quick-hardening repair mortar.

[0037] Step 4: Setting the horizontal seam

[0038] After the repair mortar applied in step 3 has initially set or hardened, regular transverse joints are set. These transverse joints are perpendicular to the track direction and extend across the entire width of the repair area. The joint spacing is 2-3 fastener spacings, calculated based on a standard fastener spacing of 600-650mm, and controlled within the range of 1.2-1.95m. The joint width is 3-5mm, and the joint depth penetrates the repair mortar layer or reaches at least 2 / 3 of the repair layer thickness. After jointing, high-pressure air is used to remove residue from the joints. After the repair mortar has fully hardened, elastic sealing material is used to fill the joints, with a filling depth of not less than 80% of the joint depth.

[0039] Step 5: Enhanced processing of critical nodes

[0040] Apply 1-2 coats of the above-mentioned special material again around the track fasteners, at the intersection of cracks, at the edge of the track bed slab, and within 100mm on both sides of the joints set in step 4 to ensure sufficient penetration and reinforcement in the joint area and to seal the gaps.

[0041] Step 6: Result Verification

[0042] After construction is completed, the effect will be inspected. The inspection standards include:

[0043] Appearance: No cracks, hollow spots, or missed areas; joints are straight; sealant is fully applied.

[0044] Strength: The surface resilience after repair is ≥20% higher than before repair;

[0045] Bond strength: The bond strength between the special material and the original concrete is ≥3.0MPa, and the bond strength between the repair layer and the base layer reinforced with the special material is ≥2.5MPa;

[0046] Joint quality: The joint spacing, joint width, joint depth and filling quality meet the requirements, and the straightness deviation of the joint is ≤5mm / 2m;

[0047] Impermeability: Impermeable pressure ≥1.0MPa.

[0048] Beneficial effects

[0049] This invention achieves significant beneficial effects through a series of synergistic technical means. Specifically, it first provides a specialized material for the inhibition and repair of pulverization in ballastless track slabs. This material is a low-viscosity (≤10 mPa·s at 25℃), highly permeable reactive organic-inorganic hybrid pulverization inhibitor that can spontaneously penetrate more than 3 mm into the concrete of track slabs with a strength grade below 40 MPa, generating a three-dimensional silica-oxygen network structure in situ and forming chemical bonds with the hydration products of the concrete. Using this specialized material solves the problems of existing repair materials, such as high viscosity, insufficient penetration depth, and the inability to fundamentally strengthen the loose matrix by only covering the surface. It achieves deep penetration and consolidation, resulting in an interfacial tensile bond strength of over 3.0 MPa, an increase in cohesion of over 150%, resistance to freeze-thaw cycles of over 300, and a chloride ion diffusion coefficient reduced to 1 / 5 to 1 / 10 of the original concrete. This fundamentally blocks the pulverization and deterioration path, significantly improving the mechanical properties and long-term durability of the repair layer.

[0050] Secondly, the repair method of this invention includes six steps: base cleaning, application of chalking inhibitor, crack and damage treatment, horizontal joint setting, key node reinforcement, and effect inspection. In the crack and damage treatment step, a fast-hardening repair mortar is used. This mortar has a 2-hour compressive strength ≥15MPa, a 24-hour compressive strength ≥30MPa, a bond strength with the reinforced base layer ≥2.5MPa, and a shrinkage rate ≤0.03%. Through the combination of the above materials and steps, the problems of cumbersome construction procedures, long curing periods (3-7 days), and inability to adapt to the rapid construction requirements of railway maintenance windows (90-240 minutes) in existing technologies are solved. The total construction time of the entire repair method is ≤2 hours, requires no large equipment, perfectly adapts to maintenance window operations, and simplifies the base surface pretreatment process (only removing ≤5mm loose floating layers), reducing damage to the original structure.

[0051] Specifically, this invention introduces a regular transverse jointing structure with a joint spacing of 2-3 fastener spacings (1.2-1.95m), a joint width of 3-5mm, and a joint depth penetrating the repair layer or at least reaching 2 / 3 of the repair layer thickness. The joints are filled with an elastic sealant (Shore A hardness 20-30, elongation at break ≥400%). This jointing structure solves the core problem of random and irregular cracking after large-area continuous pouring repairs due to constrained temperature stress and shrinkage deformation. By dividing the large-area continuous repair layer into independent sections, it effectively releases the shrinkage deformation and temperature stress caused by temperature changes and mortar hardening, reducing the interface shear stress of the repair layer by more than 40%, fundamentally preventing the generation of irregular cracks. Simultaneously, the elastic sealant adapts to deformation on both sides of the joint and prevents moisture intrusion, ensuring the long-term integrity of the repair layer. Examples demonstrate that no cracking problems occurred in the repair layer 12 months after repair.

[0052] Furthermore, this invention also applies reinforced coating treatment to key nodes (around fasteners, crack intersections, and both sides of joints) to seal weak channels for moisture intrusion; optionally, a weather-resistant protective agent can be further coated to form a composite protective system. Through the aforementioned complete set of technologies of "penetration and reinforcement - mortar repair - regular jointing," this invention not only increases the rebound strength of the repaired track slab by more than 20% and achieves a seepage resistance pressure of more than 1.0 MPa, but also can withstand train dynamic load fatigue testing at frequencies of 5-20 Hz and more than 3 million cycles, without the risk of spalling or splashing, ensuring operational safety. Compared with existing technologies, this invention avoids secondary defects such as cracking, hollowing, and peeling of the repair layer, significantly reduces the frequency of repeated maintenance, and lowers the total life cycle cost by more than 20%, achieving the technical effect of "one-time repair, long-term effectiveness."

[0053] Compared with the prior art, the penetration depth (4.2 mm) of the present invention is 3.5 times that of Comparative Example 1 (1.2 mm) and 14 times that of Comparative Example 2 (0.3 mm); the bonding strength (3.8 MPa) is 1.8 times that of Comparative Example 1 (2.1 MPa) and 2.9 times that of Comparative Example 2 (1.3 MPa); the rebound strength improvement rate after repair (27.6%) is 3.6 times that of Comparative Example 1 (7.6%) and 2.7 times that of Comparative Example 2 (10.2%); during the 12-month observation period, the present invention showed no cracks, while Comparative Example 1 showed 2 cracks and Comparative Example 2 showed 3 cracks and hollow areas. The above data fully demonstrate that the present invention has achieved significant technical progress. Attached Figure Description

[0054] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0055] Example 1

[0056] This embodiment, through systematic material screening and ratio optimization, ultimately determined an optimal embodiment of a special material for the pulverization inhibition and repair of ballastless track slabs (strength grade below 40MPa). This special material is a low-viscosity, high-penetration, reactive organic-inorganic hybrid pulverization inhibitor, composed of component A and component B mixed in a 4:1 volume ratio. Component A contains low-viscosity bisphenol F epoxy resin, butyl glycidyl ether (BGE) reactive diluent, γ-aminopropyltriethoxysilane (KH-550) silane coupling agent, and fumed silica nanoparticles with an average particle size of 30nm; component B is a composite curing accelerator composed of modified alicyclic amines and tertiary amines. Through extensive orthogonal experiments and single-factor screening, the optimal ratio was determined to be: 45 parts by weight of epoxy resin, 12 parts by weight of reactive diluent, 4 parts by weight of silane coupling agent, and 3 parts by weight of nano-silica in component A; and 3 parts by weight of composite curing accelerator in component B. After mixing, the viscosity was measured to be 9 mPa·s using an NDJ-8S rotational viscometer (rotor No. 4, 60 r / min, 25℃).

[0057] The selection of this proportion is not arbitrary, but based on the analysis of the microstructure of pulverized concrete and targeted solutions to the shortcomings of existing technologies. The capillary pore size inside the pulverized layer of the track slab is mostly less than 50 μm, the width of microcracks is often less than 0.3 mm, and the cohesion of the pulverized layer is usually less than 0.7 MPa. Existing repair materials are either too viscous to penetrate (e.g., polymer mortar particles > 100 μm) or can only adhere to the surface and cannot strengthen the matrix (e.g., silane impregnation depth < 1 mm). Therefore, this invention needs to simultaneously achieve ultra-low viscosity (≤ 10 mPa·s) and deep penetration (≥ 3 mm), and form chemical consolidation to improve bond strength and cohesion. The following details the basis for the proportions of each component, the working principle, and the use of non-common knowledge as evidence.

[0058] Regarding the ratio of epoxy resin to reactive diluent: It is generally accepted in the art that epoxy resin viscosity is typically 200-1000 mPa·s. Low viscosity implies low molecular weight and low strength, which is contradictory. This invention introduces reactive diluent and nano-silica. During the experimental screening process, the inventors set up a control ratio (40 parts epoxy resin, 15 parts diluent, 3 parts coupling agent, 2 parts nano-silica, and 2 parts curing accelerator; this ratio is for comparison only and does not constitute the scope of protection of this invention). The viscosity after mixing was 8 mPa·s, the penetration depth was 3.8 mm, and the compressive strength of the solidified layer was approximately 65 MPa. To further improve the mechanical properties, this invention attempted to increase the epoxy resin to 45 parts and reduce the diluent to 12 parts. Conventionally, this would lead to increased viscosity and decreased permeability. However, experiments revealed that due to the "ball bearing effect" of nano-silica (nanoparticles act like bearings in the resin, reducing molecular chain entanglement and frictional resistance) and the reduction of surface tension of the system by the silane coupling agent, the viscosity after mixing only increased from 8 mPa·s to 9 mPa·s, while the penetration depth increased from 3.8 mm to 4.2 mm, and the compressive strength of the consolidated layer increased to 78 MPa. This positive synergistic effect is unforeseen by those skilled in the art and constitutes an important inventive point of this invention. Simultaneously, there is an optimal window for the amount of reactive diluent: below 12 parts, the system viscosity is >12 mPa·s, and the penetration depth is <2.5 mm; above 18 parts, the crosslinking density decreases, and the bonding strength is <2.5 MPa. In this embodiment, the diluent is controlled at 12 parts, precisely at the lower edge of the window, ensuring both low viscosity and avoiding over-dilution.

[0059] Regarding the dosage of silane coupling agents: The role of silane coupling agents is to form "molecular bridges" between organic epoxy resin and inorganic concrete matrix, significantly improving interfacial bonding strength through chemical bonding. The conventional dosage in the art is 1% to 2% of the resin mass. However, X-ray photoelectron spectroscopy (XPS) analysis revealed that due to cement paste loss, the exposure rate of active hydroxyl (-OH) and silanol (Si-OH) sites on the surface of powdered concrete is three times that of ordinary concrete, requiring a higher chemical bridging density to achieve full interfacial coverage. Therefore, this invention systematically investigated coupling agent dosages of 2, 3, 4, and 5 parts. The results showed that with 2 parts, the surface Si-OC bond content was 2.5 times that of the untreated sample, with an interfacial bond strength of 3.4 MPa; with 3 parts, it was 3.2 times, with a bond strength of 3.6 MPa; with 4 parts, it reached 4.0 times (reaching a plateau), with a bond strength of 3.8 MPa, and the failure mode was cohesive failure within the substrate concrete (indicating that the bond strength was higher than that of the substrate itself); with 5 parts, due to the self-condensation of silane molecules forming multilayer physical adsorption, chemical bonding was hindered, and the bond strength dropped to 3.5 MPa. Therefore, 4 parts is the critical optimal value. Compared with the basic ratio (3 parts), this embodiment increased the coupling agent to 4 parts, increasing the bond strength from 3.6 MPa to 3.8 MPa, and reaching the substrate failure level. This critical threshold effect is not obvious.

[0060] Regarding the dosage of nano-silica: The function of nano-silica is not only to fill the nanoscale pores (5-10 nm) formed after epoxy resin curing, but more importantly, to synergistically construct an organic-inorganic interpenetrating polymer network (IPN) with silane coupling agents. Microstructures at different dosages were observed using transmission electron microscopy (TEM): At 1 part, the nanoparticles were well dispersed but failed to form a continuous network, and the cohesive force increased from approximately 0.7 MPa in the original powdered layer to 1.81 MPa (an increase of 158%); at 2 parts, the pore filling rate was approximately 85%, and a preliminary network structure appeared locally, with the cohesive force increasing to 1.85 MPa (an increase of 164%); at 3 parts, a complete IPN structure was formed, with a pore filling rate >95%, and the cohesive force increasing to 1.95 MPa (an increase of 178%); at 4 parts, the nanoparticles agglomerated (agglomerate size >200 nm), becoming stress concentration points, and the cohesive force decreased to approximately 1.89 MPa (an increase of 170%). Therefore, 3 parts is the critical point for IPN network formation; below this value, the network is incomplete, and above this value, aggregation occurs. This discovery is disclosed for the first time in this invention and can be easily obtained by those not skilled in the art through conventional experiments. The basic mix uses 2 parts nano-silica (increasing cohesion by 164%), and this embodiment uses 3 parts, further increasing it to 178%. At the same time, the chloride ion diffusion resistance coefficient is reduced from 1 / 9 of the original concrete to 1 / 10, significantly enhancing durability.

[0061] Regarding the dosage of the composite curing accelerator: This invention employs a modified alicyclic amine and tertiary amine compound system, aiming to achieve rapid curing over a wide temperature range (-10℃~35℃) to meet the construction requirements during railway maintenance windows. Differential scanning calorimetry (DSC) was used to test the curing exothermic curves at different dosages: at 2 parts, the exothermic peak was 48℃, with curing time approximately 4 hours; at 3 parts, the exothermic peak was 52℃, with curing time approximately 3 hours; at 4 parts, the exothermic peak was 68℃, approaching the concrete thermal damage threshold of 70℃. Furthermore, excessively rapid curing (surface dry <2 hours) caused the inhibitor to gel before fully penetrating the concrete, thus reducing penetration depth and bonding effect. Therefore, 3 parts is the optimal upper limit, ensuring normal curing at -10℃ (surface dry ≤6 hours) and preventing explosive polymerization at 35℃, while the curing time (3 hours) perfectly matches the maintenance window period (90-240 minutes). The basic mix ratio is 2 parts (curing takes about 4 hours), while this example uses 3 parts, which further shortens the construction waiting time, and the safety was verified by DSC.

[0062] The composition of the matching quick-setting repair mortar. To work synergistically with the aforementioned special materials, the quick-setting repair mortar in this embodiment consists of: 100 parts by weight of quick-setting sulfoaluminate cement, 75 parts by weight of 0.1-1.0mm graded quartz sand, 6 parts by weight of styrene-acrylic polymer emulsion, 1.0 part by weight of basalt crack-resistant fiber, 0.6 parts by weight of polycarboxylate superplasticizer, and 7 parts by weight of ettringite-based expansion agent. This mortar has a 2-hour compressive strength of 17.5 MPa, a 24-hour compressive strength of 32.8 MPa, a bond strength of 3.8 MPa with the substrate reinforced by the special materials, and a 90-day shrinkage rate of only 0.019%.

[0063] Performance test results. Following standard testing methods, the performance of the special materials and matching mortar in this embodiment is as follows: penetration depth 4.2mm (measured under a microscope after cutting); interfacial tensile bond strength 3.8MPa (pull-out test, failure mode was cohesive failure of the base concrete); cohesion increased by 178% (in-situ pull-out method); rebound strength of the repaired track slab increased by 27.6% compared to before repair; strength retention rate after 300 freeze-thaw cycles 93%; chloride ion diffusion coefficient reduced to 1 / 10 of the original concrete (RCM method); passed 3 million fatigue tests (frequency 5-20Hz) without any spalling or chipping.

[0064] Comparison with comparative examples. To verify the inventiveness of this embodiment, comparative examples 1-3 were set up. Comparative example 1 used nano-silica sol (solid content 25%, viscosity approximately 50 mPa·s) from patent CN104987027B, without matching early-strength repair mortar, and without jointing. Test results: penetration depth 1.2 mm, bond strength 2.1 MPa, rebound strength increase 7.6%, 90-day shrinkage rate 0.042%, 300-cycle freeze-thaw retention rate 78.3%, and 2 cracks appeared after 12 months. Comparative example 2 used ordinary polymer-modified cement mortar (styrene-butadiene emulsion + cement + sand), without using penetration inhibitors, and without jointing. Test results: penetration depth 0.3 mm, bond strength 1.3 MPa, 2-hour compressive strength 8.5 MPa, 90-day shrinkage rate 0.058%, rebound strength increase 10.2%, and 3 cracks and hollow areas appeared after 12 months. Comparative Example 3 used isooctyltriethoxysilane impregnating agent, without mortar repair or jointing. Test results: penetration depth 0.8mm, bond strength 1.8MPa, rebound strength improvement 5.8%, no defect repair capability, and protective effect less than 5 years. This example is significantly superior to the comparative example in penetration depth (4.2mm), bond strength (3.8MPa), mechanical strength improvement (27.6%), shrinkage control (0.019%), freeze-thaw durability (93% retention rate), and long-term crack resistance (no cracks for 12 months), and all indicators meet or even exceed the technical requirements for railway track slab repair.

[0065] In summary, this embodiment, through precise formulation design (45 parts epoxy resin, 12 parts diluent, 4 parts silane coupling agent, 3 parts nano silica, and 3 parts curing accelerator), utilizes the nonlinear synergistic effect between components (the ball-bearing effect and IPN network construction of nano silica, the critical full coverage of the silane coupling agent, and the temperature control window of the curing accelerator) to achieve deep penetration (4.2 mm) and high consolidation strength (78 MPa) at low viscosity (9 mPa·s). Interfacial adhesion reaches the level of substrate failure, cohesion is increased by 178%, and overall durability performance is excellent. The above formulation parameters and technical effects are not common knowledge in the field, but rather critical optimal values ​​obtained through cross-validation using multiple methods such as XPS, TEM, and DSC.

[0066] Example 2

[0067] This embodiment provides a method for inhibiting and repairing pulverization of ballastless track slabs using the aforementioned specialized materials. This method is designed based on an in-depth analysis of the development patterns of ballast slab pulverization and the shortcomings of existing technologies. Its core innovation lies in constructing a standardized repair process of "penetration and strengthening—mortar repair—regular jointing." Steps 2 (powdering inhibitor application) and 3 (crack and damage treatment) are key steps in solving the problem of strengthening low-strength, loose matrix. Step 4 (transverse jointing) is an original method for fundamentally addressing large-area repair layer cracking from a structural perspective. The following details each step.

[0068] Step 1: Base cleaning

[0069] The technical objective of this step is to create open channels for inhibitor penetration while minimizing damage to the original structure. Existing techniques typically involve large-area chiseling or high-pressure water jet cleaning, which is not only time-consuming and labor-intensive but also further damages the already fragile powdery layer. This invention, through extensive experimentation, has discovered that the powdery layer of the track slab can be divided into three zones from the surface inwards: a completely loose surface zone (0-5mm thick, aggregate and slurry separated, cohesion close to zero), a transition zone (5-15mm thick, some cement hydration products still present, cohesion approximately 30%-50% of the original strength), and a healthy zone (below 15mm, normal cohesion). Excessive removal into the transition zone or even the healthy zone not only significantly increases the workload but also damages the original load-bearing structural layer, constituting "over-treatment." This invention only removes the loose surface layer (removal thickness ≤ 5mm) because this layer contributes no structural value, and its loose, porous structure hinders the penetration of inhibitors into the lower transition zone—loose particles absorb inhibitors like a "sponge" but cannot form effective consolidation, instead consuming material. Removing more than 5mm exposes the deeper, relatively dense concrete, thus reducing the thickness of the loose layer that the inhibitor can penetrate. Insufficient removal (<2mm) leaves surface dust and loose particles unremoved, continuing to clog pores. Therefore, 5mm is the optimal upper limit determined through extensive removal of track slabs with varying degrees of pulverization. The remaining transition zone after removal contains interconnected pores (10-50μm in diameter), an ideal medium for deep penetration of the inhibitor. Grinding is performed using an angle grinder equipped with a diamond grinding disc (80-120 mesh). The ultra-high hardness of diamond efficiently removes the loose layer, while the flat bottom of the grinding disc ensures uniform removal thickness. After cleaning, a high-pressure blower with a pressure ≥0.6MPa is used to blow along the track direction. This pressure was determined through testing: below 0.6MPa, fine dust particles with a diameter of 10-30μm embedded in the pores cannot be removed, and these dust particles will block the pore entrance like a "plug"; above 1.0MPa, it may blow off aggregates that have not yet been completely loosened in the transition zone. The moisture content of the base layer is controlled at ≤10%, which is based on the balance between the hydrolysis requirements of the silane coupling agent and the replacement of the water film by the inhibitor: the silane coupling agent requires about 2%-5% pore water to hydrolyze and generate silanol groups, but if the moisture content exceeds 10%, a continuous water film will form on the pore surface, and the organic components of the inhibitor (surface tension about 32mN / m) cannot effectively replace the water film (surface tension of water 72mN / m), resulting in stagnant penetration. Experiments showed that the inhibitor penetration depth was greatest (≥4mm) when the moisture content was 6%-10%; when the moisture content was ≤5%, the coupling agent hydrolyzed insufficiently, resulting in a decrease in bonding strength of approximately 15%; and when the moisture content was >12%, the penetration depth decreased to below 2mm. Therefore, this step precisely controls the moisture content between 6% and 10% through natural air drying or hot air drying, ensuring both the hydrolysis reaction of the coupling agent and creating conditions for penetration.

[0070] Step 2: Apply chalking inhibitor

[0071] This step is the core of this invention, achieving a three-in-one function of "ultra-low viscosity + deep penetration + chemical consolidation," fundamentally solving the industry problem of the inability to strengthen low-strength, porous matrices. In existing technologies, polymer mortars with a viscosity >500 mPa·s can only provide surface coverage; silane impregnating agents, although having low viscosity (approximately 5 mPa·s), lack consolidation ability; and nano-silica sols with a viscosity of approximately 50 mPa·s rely on unhydrated cement for activation, rendering them ineffective against powdery layers. This invention, through the design of specialized materials, controls the viscosity at 25℃ to ≤10 mPa·s (as shown in Example 1, 9 mPa·s provides the best overall performance), while also possessing reactive consolidation capabilities. The basis for this viscosity limitation is as follows: penetration depth tests were conducted using epoxy systems of different viscosities. The results showed that when the viscosity was ≤10 mPa·s, spontaneous penetration depth ≥3 mm could be achieved within 30 minutes; when the viscosity was 12-15 mPa·s, the penetration depth decreased to 2-2.5 mm; and when the viscosity was >20 mPa·s, the penetration depth was less than 1 mm. Therefore, ≤10 mPa·s is a necessary condition for achieving deep permeation.

[0072] Component A and component B of the special material are mixed at a volume ratio of 4:1. This ratio was determined through curing reaction kinetics calculations and extensive experiments. The epoxy equivalent of the epoxy resin in component A is approximately 190 g / eq, and the amine value of the composite curing accelerator in component B is approximately 350 mg KOH / g. When mixed at 4:1, the molar ratio of epoxy groups to active hydrogen is close to 1:1, ensuring complete curing and no excess reactants remaining. After mixing, use a handheld electric stirrer to stir at a high speed of 500-800 rpm for 3-5 minutes. The stirring speed and time must be strictly controlled: stirring speeds below 500 rpm or for less than 3 minutes will result in uneven mixing of components A and B, and insufficient local curing; stirring speeds above 800 rpm or for more than 5 minutes will introduce a large number of air bubbles (because the system viscosity is low, air bubbles do not easily escape). These air bubbles enter the pores and solidify to form cavities, which become new defects. After stirring, let it stand for 1-2 minutes to defoam, and use it within 30 minutes, because the usable period of the mixed system at 25°C is about 40 minutes (the time it takes for the viscosity to rise to 20 mPa·s). After 30 minutes, the viscosity has increased significantly and the penetration depth has decreased.

[0073] Short-nap rollers (8-10mm bristle length) are chosen for the following reasons: Brush bristles that are too soft cannot force the pressure into the pores, while bristles that are too hard will scratch the surface; while spraying is efficient, solvent evaporation during droplet flight increases viscosity and can cause splashing and contamination of fasteners. Short-nap rollers generate approximately 0.01-0.03MPa of contact pressure during rolling, forcing the inhibitor into the pore openings. Simultaneously, the roller's porous structure ensures even liquid release, preventing localized liquid accumulation. The application method is 2-3 coats, alternating between horizontal and vertical strokes. The specific mechanism is as follows: During the first horizontal coat, the inhibitor mainly diffuses horizontally, filling the surface pores; after a 10-15 minute interval, the second vertical coat is applied. By this time, the first coat's inhibitor has partially penetrated (approximately 1-2mm deep) but is not yet fully cured. The shear force of the vertical coat disrupts the surface tension balance of the existing penetration channels, allowing the inhibitor to continue penetrating vertically; the third coat is applied to areas with uneven absorption, increasing the amount locally to ensure full overall penetration. The 10-15 minute interval between each coat is based on the penetration rate calculation: the penetration rate of the inhibitor in powdery concrete is approximately 0.1-0.2 mm / min. In 10-15 minutes, it can penetrate 1-2 mm. At this point, the surface is not yet dry (it still has a moist sheen), allowing the second coat to form a continuous wet film with the first, preventing delamination. If the interval is shorter than 10 minutes, the previous coat will not have fully penetrated and will be covered, causing surface buildup; if the interval is longer than 15 minutes, the surface may begin to gel, preventing the second coat from achieving continuous penetration.

[0074] The application rate is 0.4-0.6 kg / m². 2 The severely pulverized area can increase to 0.8 kg / m². 2 The dosage is determined based on the following: the porosity of the transition zone of the pulverized layer in the track slab is typically 15%-25%. Assuming 20%, to achieve a 3mm penetration depth, the required pore volume per square meter is 0.2 × 0.003 × 1 × 10⁻⁶. 6 =600cm 3 The inhibitor density is approximately 1.1 g / cm³. 3 The theoretical mass is 660g. However, during the actual infiltration process, some pores are occupied by residual moisture and air, and the volume shrinkage after the inhibitor solidifies is about 0.1%-0.3%, therefore the actual mass is 0.4-0.6kg / m³. 2 This is the optimal value based on experience. When the dosage is below 0.4 kg / m², the penetration depth is less than 2.5 mm; when the dosage is above 0.8 kg / m², the penetration depth is less than 2.5 mm. 2 If an excessively thick liquid film forms on the surface, microcracks are likely to occur after solidification. For severely pulverized areas (porosity > 25%), the concentration needs to be increased to 0.8 kg / m³. 2Ensure thorough filling. Closely observe the penetration during application, and reapply promptly when dry, discolored areas appear on the surface. This is because the pore distribution in the chalking layer is uneven—at the intersection of cracks or near original air bubbles, large pores (>100μm) act like "siphons," rapidly drawing away the inhibitor, causing premature drying of localized areas. If not reapplied in time, these large pores cannot be filled and will become channels for water seepage later.

[0075] The final standard for full penetration is defined as "the adhesive stops seeping and the substrate exhibits a continuous, moist, and glossy appearance." This indicates that all interconnected pores have been filled with the inhibitor, forming a continuous liquid film approximately 0.1 mm thick on the surface. This standard is based on the following phenomenon: when pores are not completely filled, the inhibitor continues to seep, and the surface liquid film is absorbed into the pores, forming localized dry patches; when the pores are completely filled, excess inhibitor has nowhere to go and spreads on the surface to form a continuous film. At this point, the total penetration depth has been achieved, measured to be 3.5-4.2 mm (depending on the mixing ratio), meeting the requirement of ≥3 mm. After this step, the inhibitor dries on the surface within 4 hours. During this period, the silanol groups generated by the hydrolysis of the silane coupling agent undergo a condensation reaction with the active hydroxyl groups on the concrete surface, forming Si-O-Si covalent bonds; simultaneously, the epoxy resin undergoes ring-opening polymerization under the action of the curing accelerator, forming a three-dimensional cross-linked network; and nano-silica participates in the construction of an organic-inorganic interpenetrating network (IPN). The cured structure firmly bonds the loose aggregates, increasing the cohesion in the transition zone from below 0.7 MPa to above 1.85 MPa (an increase of >150%). The measured interfacial tensile bond strength is ≥3.0 MPa (maximum 3.8 MPa). Simultaneously, it blocks capillary pores, reducing the chloride ion diffusion resistance coefficient to 1 / 10 of its original value. This process effectively blocks the pulverization and degradation pathway at its source, rather than relying on surface masking as in traditional methods.

[0076] Step 3: Repairing Cracks and Damage

[0077] This step, together with step 2, forms a synergistic system, achieving a division of labor between "deep penetration and consolidation" and "precise reinforcement of surface defects." Existing technologies often attempt to solve both penetration and repair problems simultaneously with a single material, but low-viscosity materials cannot fill large cavities, and high-viscosity materials cannot penetrate micropores. This invention employs a graded treatment strategy, in which the accompanying fast-hardening repair mortar is crucial.

[0078] After the inhibitor applied in step 2 has dried to a surface (approximately 4 hours), it has essentially cured, forming a reinforced base layer, but has not yet reached full strength (approximately 60% of the final strength). The reason for this timing is that if repairs are made after the inhibitor has fully cured (24 hours), the surface will be too smooth, and the bond between the repair mortar and the reinforced base layer will primarily rely on physical anchoring. However, when the inhibitor is not fully cured, the moisture and active ingredients in the repair mortar can continue to react with the unreacted functional groups on the inhibitor surface, forming chemical bonds and increasing the bond strength from 2.5 MPa to 3.8 MPa. Cracks and damaged areas on the track slab are treated in stages: for fine cracks <1.0 mm wide, the cured inhibitor will fill them automatically without additional treatment. This is because the inhibitor's low viscosity (9 mPa·s) and low surface tension (32 mN / m) allow it to penetrate cracks as narrow as 0.1 mm through capillary action. The resulting IPN structure after curing firmly bonds the crack walls, restoring its tensile strength. Experiments have shown that after filling a 0.5mm wide crack with an inhibitor, the splitting tensile strength can reach more than 85% of the original concrete. For wide cracks ≥1.0mm and obvious defects, rapid-hardening repair mortar is used for filling and compaction. The formulation of this repair mortar reflects its synergy with the inhibitor: rapid-hardening sulfoaluminate cement provides early strength (≥15MPa at 2h), meeting the requirements for opening to traffic during the maintenance window; the 0.1-1.0mm quartz sand gradation gives the mortar good workability and low shrinkage; polymer emulsion (styrene-butadiene, styrene-acrylic, or VAE) improves bond toughness and crack resistance; crack-resistant fibers (polypropylene or basalt) prevent plastic shrinkage cracks; and the expansion agent (ettringite-based) compensates for chemical shrinkage, resulting in a 90-day shrinkage rate ≤0.03%. In particular, the bond strength between this mortar and the inhibitor-reinforced substrate is ≥2.5MPa. This is because the surface of the cured inhibitor contains unreacted epoxy and silanol groups, which can undergo cross-linking reactions with the polymer emulsion in the mortar to form a chemical anchor. Layered construction with each layer ≤10mm thick is based on the following principles: The heat release during hydration of sulfoaluminate cement is concentrated; if a single layer is too thick (e.g., >20mm), the internal temperature can rise above 50℃, causing rapid surface moisture evaporation and making it prone to temperature cracks and plastic shrinkage cracks. During layered construction, each layer is compacted with a trowel before initial setting to remove air bubbles and enhance interlayer adhesion. Simultaneously, the upper layer is constructed only after the hydration heat of the lower layer has been released, avoiding heat accumulation. Experiments show that the shrinkage crack incidence rate is <1% with each 10mm layer, while it rises to 15% with each 20mm layer. For exposed rusted rebar, rust must first be removed with a wire brush to St2 grade (no visible grease, dirt, or loose rust), followed by application of an anti-rust primer (epoxy zinc-rich or water-based acrylic). The loose rust (Fe2O3·nH2O) on the surface of rusted rebar can expand to 6-10 times its original size. If rust is not removed before wrapping, the rust will continue to expand under wet-dry cycles, cracking the repair layer.After the anti-rust primer has dried for about 30 minutes, cover it with repair mortar, ensuring there are no cavities around the reinforcing bars and that the bond strength between the repair mortar and the reinforcing bars is ≥1.5MPa. For continuous large-area repair areas (length >2m), apply the repair mortar continuously in one go, keeping the surface smooth to prepare for subsequent jointing.

[0079] Step 4: Setting the horizontal seam

[0080] This step is a unique structural design that distinguishes this invention from existing technologies. Existing technologies all employ large-area continuous casting, failing to consider the elongated, thin-walled structural characteristics of the track slab. The surface temperature of the track slab can reach 60°C under sunlight, dropping below 0°C at night; the coefficient of linear expansion caused by this temperature change is approximately 10 × 10⁻⁶. -6 At ℃, for a repair layer 10m in length, a temperature change of 50℃ can result in a free expansion and contraction of up to 5mm. If the repair layer is fully bonded to the base layer, this expansion and contraction is constrained, generating tensile stress within the repair layer. The magnitude of the tensile stress is σ=E·α·ΔT, where E is the elastic modulus of the repair mortar (approximately 20GPa), and α is the coefficient of linear expansion (10×10⁻⁶). -6 With a temperature of ΔT=50℃, the calculated σ=10MPa, while the tensile strength of the repair mortar is only 2-3MPa, inevitably leading to cracking. This invention divides the continuous repair layer into independent sections by setting regular transverse joints. Each section is 1.2-1.95m long, corresponding to a free expansion and contraction of 0.6-1.0mm, far less than the joint width of 3-5mm. Therefore, the expansion and contraction deformation is absorbed by the joint, and no tensile stress is generated within the section.

[0081] The basis for limiting the joint spacing to 2-3 fastener spacings (1.2-1.95m) is as follows: the standard fastener spacing is 600-650mm. When the spacing is less than 1.2m (less than 2 fastener spacings), the joints are too dense, reducing construction efficiency and increasing the amount of sealant used. Additionally, if each panel is too short, the fastener constraint overlaps, potentially causing localized stress concentration. When the spacing is greater than 1.95m (more than 3 fastener spacings), the panels are too long, and the calculated temperature stress in the central area may still exceed the tensile strength of the repair mortar (when the panel length > 2m, the maximum tensile stress at the center is approximately 2.5-3.0MPa, close to the limit). Through finite element simulation and field experiments, the maximum tensile stress within the panels within the 1.2-1.95m range is ≤1.5MPa, with a safety factor ≥1.5. The specific value can be adjusted according to the on-site temperature conditions—take a smaller value (1.2m) in the high-temperature season because the temperature of the repair layer is high after summer construction, and the amount of shrinkage due to cooling is large; take a larger value (1.95m) in the low-temperature season because the amount of expansion due to temperature rise after winter construction is relatively small.

[0082] The reason for limiting the joint width to 3-5mm is as follows: If the joint width is too narrow (<3mm), the concrete on both sides may come into contact during expansion, transferring compressive stress and causing the joint edge to crush; if it is too wide (>5mm), the sealant will deform significantly and is prone to fatigue tearing. This is based on a maximum slab length of 1.95m, a temperature difference of 50℃, and a linear expansion coefficient of 10×10⁻⁶. -6 Calculated at / ℃, the maximum expansion / contraction is 1.95×10×10 -6 ×50≈0.98mm. Considering construction errors and long-term creep, a safety factor of 3-5 is adopted. A joint width of 3-5mm can completely absorb deformation without causing contact between the two sides. At the same time, the elongation at break of the sealant is ≥400%, and the strain is about 40%-67% under ±2mm deformation, which is far below the limit value, ensuring long-term sealing.

[0083] The basis for determining the joint depth to penetrate the repair mortar layer or reach at least 2 / 3 of the repair layer thickness is that shallow joints (<1 / 2 thickness) cannot release the tensile stress at the bottom, and cracks may still initiate from the bottom of the joint and penetrate through it. Stress analysis shows that when the joint depth reaches 2 / 3 of the thickness, the residual tensile stress at the bottom is less than 0.5 MPa (less than 20% of the tensile strength of the repair mortar), which will not lead to cracking. Experiments show that when the joint depth / thickness ratio is 0.67, no cracks appear after 100 temperature cycles; when the ratio is 0.5, cracks appear after 40 cycles.

[0084] The joint must be located away from directly below the fasteners, ideally in the middle of the fastener gap. Fasteners are the most critical stress points on the track slab. If the joint is directly below the fastener, it weakens the integrity of the fastener area, leading to changes in track geometry. When located in the middle of the fastener gap, the track is constrained by fasteners on both sides, resulting in better stability. After cutting the joint, use high-pressure air (≥0.6MPa) to remove any residue, ensuring no dust or debris remains; otherwise, the sealant will not adhere to the joint wall. After the repair mortar has fully hardened (24 hours after application), fill the joint with an elastic sealant, ensuring the filling depth is no less than 80% of the joint depth. This limit is based on the following: if the filling depth is less than 80%, the bottom cavity is too large, and the sealant is easily pulled out or torn when deformed; if the filling is too full (100%), the surface is easily squeezed out by wheel pressure. 80% is the optimal value, ensuring both bonding depth and allowing for deformation buffer space. The sealant is made of polyurethane or silane-modified polyether with a Shore A hardness of 20-30. This allows it to withstand wheel pressure (too low a hardness makes it easily extruded) while maintaining sufficient flexibility (too high a hardness restricts deformation). It has an elongation at break ≥400% and a temperature resistance of -40℃ to +80℃, covering all climate zones nationwide. When filling the joint, use a caulking gun to press the sealant into the bottom of the joint, filling from bottom to top to avoid air bubbles. Smooth the surface, creating a concave surface slightly lower than the repair layer surface (approximately 0.5mm) to prevent direct wheel pressure on the sealant.

[0085] Step 5: Enhanced processing of critical nodes

[0086] The areas around fasteners, crack intersections, and the sides and edges of joints in the track slab are weak points prone to stress concentration and moisture intrusion. When fasteners transfer train loads, local compressive stress (up to 5-10 MPa) and shear stress are generated at the contact surface between the fastener base and the track slab. If the penetration in this area is insufficient, the stress will diffuse along the interface, leading to delamination. Crack intersections are concentration points of original structural damage, and even after repair, micro-unfilled channels may still exist. Although sealant is applied to both sides of the joints, the interface between the sealant and the repair layer remains a potential water seepage path. In this step, 1-2 coats of a special material are applied again to these critical areas, utilizing its low viscosity (9 mPa·s) and strong penetrability to further seal micro-defects. The rationale for applying 1-2 coats is: one coat can cover the surface, but there may be omissions; two coats ensure 100% coverage and a certain thickness; more than two coats waste material, and an excessively thick surface after curing may affect the flatness. The reinforcement range is 100mm on each side of the joint. This range is determined by calculating the stress diffusion angle: the width of the stress-affected zone at the joint edge is approximately 5-10 times the thickness of the slab (slab thickness 15-20mm, affected zone approximately 75-200mm). A 100mm range can completely cover the high-stress area. Specifically, a 50mm wide inhibitor sealing treatment is added to the joint edge, allowing the sealant to bond directly to the inhibitor reinforcement layer, rather than to the repair mortar. This is because the surface energy of the inhibitor reinforcement layer (approximately 45mN / m) is higher than that of the repair mortar (approximately 30mN / m), resulting in better compatibility with the sealant (surface energy approximately 35mN / m), and the bonding strength can be increased by more than 30%. The contact surface between the fastener base and the track slab is brushed with a concentrated layer of inhibitor; the stiff bristles of the brush can squeeze the inhibitor into the gaps of the contact surface, forming a continuous waterproof membrane.

[0087] Step 6: Result Verification

[0088] This step establishes quantitative acceptance standards to ensure traceability of repair quality. Visual inspection requires no cracks, hollow areas, or missed areas; joints must be straight; and sealant must be fully applied. Strength testing uses a rebound hammer, measuring 16 points per square meter and taking the average. The repaired area should show an improvement of ≥20% compared to the original (this indicator is based on railway maintenance specifications, and the measured improvement in this example was 27.6%). Bond strength testing uses a pull-out tester. The bond strength between the special material and the original concrete should be ≥3.0 MPa (this value was determined through numerous pull-out tests; when the bond strength is ≥3.0 MPa, the failure mode is cohesive failure of the base concrete, indicating that it exceeds the strength of the base material itself); the bond strength between the repair layer and the reinforced base layer should be ≥2.5 MPa (this value ensures the repair layer does not peel off under train vibration). Joint quality inspection uses a 2m straightedge and feeler gauge; straightness deviation ≤5mm / 2m (this tolerance refers to concrete construction acceptance specifications, ensuring neat joints and uniform sealant filling). The impermeability test is conducted using the dripping method or an impermeability tester. When dripping water, the water forms beads that roll without penetrating. The impermeability pressure is ≥1.0MPa (this value corresponds to the P10 impermeability grade, which meets the waterproof requirements of the track bed slab).

[0089] Step 7 (optional): Construction of flexible protective layer

[0090] For extreme environments (such as coastal areas with high salt spray, frequent freeze-thaw cycles in cold regions, and high-altitude areas with strong ultraviolet radiation), a layer of weather-resistant protective agent can be applied after the above steps are completed and fully cured (within 1-7 days). This protective agent is a silicone-modified acrylic or fluorocarbon transparent coating, applied by spraying at a dosage of 0.3-0.5 kg / m². Its function is to form a dense hydrophobic film (water contact angle > 110°) on the surface of the repair layer, further blocking ultraviolet rays and salt spray, while not affecting the appearance of the track bed slab and the coefficient of friction (coefficient of friction > 0.6). Special attention should be paid to spraying at joints to ensure continuous protection between the sealant and the protective agent.

[0091] The above method, through a six-step collaborative process, achieves the following technical effects: total construction time ≤ 2 hours (average 1.8 hours from cleaning to inspection completion, based on on-site timing), perfectly suited for railway maintenance windows (90-240 minutes); measured inhibitor penetration depth ≥ 3mm (4.2mm); interfacial tensile bond strength ≥ 3.0MPa (3.8MPa); cohesion increased by 178% ≥ 150%; rebound strength after repair increased by 27.6% ≥ 20%; joint straightness deviation ≤ 3mm / 2m ≤ 5mm / 2m; impermeability pressure ≥ 1.5MPa ≥ 1.0MPa; 93% retention rate after 300 freeze-thaw cycles; chloride ion diffusion coefficient reduced to 1 / 10 of the original; no spalling after 3 million fatigue cycles. Compared with the comparative example, this method is significantly superior to the existing technology in all indicators, and all parameter limitations have clear experimental or theoretical basis, ensuring the feasibility and inventiveness of this invention.

[0092] In summary, this invention addresses the powdering and spalling defects in ballastless track slabs (especially concrete with a strength grade below 40 MPa), systematically solving five core technical problems inherent in existing repair technologies: mismatch between material permeability and consolidation capacity, insufficient construction efficiency and adaptability to maintenance windows, inadequate repair depth and root cause treatment, poor interfacial bonding and structural synergy, and lack of joint control and crack prevention. Through a powdering inhibitor, it achieves a three-in-one function of "ultra-low viscosity (≤10 mPa·s) + deep penetration (≥3 mm) + chemical consolidation," enabling the material to spontaneously penetrate into the capillary pores and microcracks within the track slab, generating a three-dimensional silica-oxygen network in situ and forming chemical bonds with concrete hydration products. This firmly bonds loose aggregates, increasing cohesion by ≥150% and achieving an interfacial tensile bond strength of ≥3.0 MPa, thus fundamentally blocking the powdering and deterioration path. The system combines fast-hardening repair mortar with inhibitors to form a synergistic effect, achieving a compressive strength of ≥15MPa in 2 hours, ≥30MPa in 24 hours, a shrinkage rate of ≤0.03%, and a bond strength with the reinforced base layer of ≥2.5MPa. This enables precise reinforcement of damaged areas and prevents secondary cracking. An innovative, regular transverse jointing structure (spacing 1.2-1.95m, joint width 3-5mm, filled with elastic sealant) divides the large-area continuous repair layer into independent sections, releasing temperature stress and shrinkage deformation. This reduces the interface shear stress of the repair layer by more than 40%, fundamentally solving the industry problem of irregular cracking in large-area repair layers. The standardized repair process of "penetrating reinforcement - mortar repair - regular jointing" simplifies the process, requires no large equipment, and has a total construction time of ≤2 hours, perfectly meeting the 90-240 minute track maintenance window requirements of railways and significantly reducing operational disruption. System verification shows that the repaired track slab exhibits a ≥20% increase in rebound strength, ≥300 freeze-thaw cycles, a chloride ion diffusion coefficient reduced to 1 / 5-1 / 10 of the original concrete, ≥5000 hours of UV aging resistance, and passes 3 million fatigue cycles (frequency 5-20Hz). There is no risk of spalling or debris falling off, and the total life-cycle cost is reduced by more than 20% compared to existing technologies, achieving the expected goal of "one-time repair, long-term effectiveness." The material-structure-process synergistic technology system proposed in this invention represents a breakthrough in the field of pulverization suppression and repair of high-speed railway ballastless track slabs, demonstrating significant inventiveness and industrial applicability.

[0093] Many specific details have been set forth in the foregoing description to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed above. Furthermore, any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A special material for inhibiting and repairing pulverization of ballastless track slabs, characterized in that, The special material is a low-viscosity, high-permeability, reactive organic-inorganic hybrid powdering inhibitor. Its viscosity at 25°C is ≤10mPa·s. It can spontaneously penetrate into the interior of track bed concrete with a strength grade of less than 40MPa, with a penetration depth of ≥3mm, and generate a three-dimensional silicon-oxygen network structure in situ. It forms chemical bonds with the concrete hydration products to achieve the integration of "penetration-filling-consolidation-reinforcement". The special material comprises component A and component B by volume ratio, wherein the mixing ratio of component A to component B is 4:1, wherein: The A component comprises: 38-45 parts by weight of low viscosity epoxy resin, 12-18 parts by weight of reactive diluent, 2-4 parts by weight of silane coupling agent, and 1-3 parts by weight of nano-reinforcing filler. Component B comprises: 2-3 parts by weight of a composite curing accelerator; After curing, the special material has a tensile bond strength of ≥3.0MPa with concrete with a strength grade of 40MPa or below, and increases the cohesion of the repaired track slab concrete by ≥150%, has a freeze-thaw cycle resistance of ≥300 times, and reduces the chloride ion diffusion coefficient to 1 / 5 to 1 / 10 of the original concrete.

2. A method for inhibiting and repairing pulverization of ballastless track slabs using the special material described in claim 1, characterized in that, The method includes the following steps: Step 1: Base cleaning For areas of pulverized track slabs, locally remove loose surface layers with a thickness ≤5mm, retaining a solid base layer; use a high-pressure blower to clean away dust, debris, and oil stains, ensuring the base layer is dry, clean, free of loose particles and standing water, with a moisture content ≤10%; Step 2: Apply chalking inhibitor After mixing component A and component B of the special material evenly at a volume ratio of 4:1, apply the mixture 2-3 times with a short-nap roller on the cleaned base layer in a crisscross pattern, with an interval of 10-15 minutes between each application. The application rate is 0.4-0.6 kg / m². Continue until the adhesive stops seeping and the base surface shows a continuous wet gloss, forming a fully penetrated standard, allowing the inhibitor to penetrate the base layer ≥3 mm. Step 3: Repairing Cracks and Damage After the inhibitor applied in step 2 has dried to the touch, the cracks and damaged areas on the track bed slab should be graded and treated accordingly: For fine cracks with a width of <1.0mm, they can be filled by the already penetrated and cured inhibitor without any additional treatment; For wide cracks ≥1.0mm and obvious defects, use quick-hardening repair mortar to fill and compact them, apply in layers, each layer ≤10mm thick, and ensure that the surface is flush with the original track bed slab. For exposed rusted steel bars, first use a wire brush to remove the rust, then apply an anti-rust primer, and after the primer is surface dry, wrap and cover it with quick-hardening repair mortar. Step 4: Setting the horizontal seam After the repair mortar applied in step 3 has initially set or hardened, regular transverse joints are set. These transverse joints are perpendicular to the track direction and extend across the entire width of the repair area. The joint spacing is 2-3 fastener spacings, calculated based on a standard fastener spacing of 600-650mm, and controlled within the range of 1.2-1.95m. The joint width is 3-5mm, and the joint depth penetrates the repair mortar layer or reaches at least 2 / 3 of the repair layer thickness. After jointing, high-pressure air is used to remove residue from the joints. After the repair mortar has fully hardened, elastic sealing material is used to fill the joints, with a filling depth of not less than 80% of the joint depth. Step 5: Enhanced processing of critical nodes Apply 1-2 coats of special material again around the track fasteners, at the intersection of cracks, at the edge of the track bed slab, and within 100mm on both sides of the joints set in step 4 to ensure sufficient penetration and reinforcement in the joint area and to seal the gaps. Step 6: Result Verification After construction is completed, the effect will be inspected. The inspection standards include: Appearance: No cracks, hollow spots, or missed areas; joints are straight; sealant is fully applied. Strength: The surface resilience after repair is ≥20% higher than before repair; Bond strength: The bond strength between the special material and the original concrete is ≥3.0MPa, and the bond strength between the repair layer and the base layer reinforced with the special material is ≥2.5MPa; Joint quality: The joint spacing, joint width, joint depth and filling quality meet the requirements, and the straightness deviation of the joint is ≤5mm / 2m; Impermeability: Impermeable pressure ≥1.0MPa.

3. The method according to claim 2, characterized in that, The rapid-hardening repair mortar described in steps 3 and 4 is composed of the following components: rapid-hardening sulfoaluminate cement, quartz sand with a particle size of 0.1-1.0 mm, polymer emulsion, crack-resistant fiber, high-efficiency water-reducing agent, and expansion agent; the rapid-hardening repair mortar has a 2-hour compressive strength ≥15 MPa, a 24-hour compressive strength ≥30 MPa, a bonding strength with the substrate reinforced by the special material described in claim 1 ≥2.5 MPa, and a shrinkage rate ≤0.03%.

4. The method according to claim 2, characterized in that, The transverse seam mentioned in step 4 is cut by a cutting machine or left in the form of a pre-cut seam; the elastic sealing material is a polyurethane or silane-modified polyether elastic sealant with a Shore A hardness of 20-30, tensile strength ≥0.6MPa, elongation at break ≥400%, and temperature resistance range of -40℃ to +80℃.

5. The method according to claim 2, characterized in that, The method further includes step 7 after step 6: construction of a flexible protective layer, that is, within 1-7 days after the special materials, repair mortar and joint structure have been fully cured, a layer of weather-resistant protective agent is applied to form a composite system of "penetrating and strengthening + precise reinforcement + regular joints + flexible protection".

6. The method according to claim 2, characterized in that, In step 2, for severely chalking areas, the amount of the special material applied is increased to 0.8 kg / m²; in step 3, for continuous large-area repair areas, the repair mortar is continuously laid in one go to keep the surface flat.

7. The method according to claim 2, characterized in that, An angle grinder equipped with a diamond grinding disc was used for grinding and removal, and a high-pressure blower with a pressure ≥0.6MPa was used for cleaning.

8. The method according to claim 2, characterized in that, Adjust the joint spacing according to the on-site temperature conditions: take the smaller value of 1.2m in the high-temperature season and the larger value of 1.95m in the low-temperature season.

9. The method according to claim 2, characterized in that, The horizontal seam is positioned away from directly below the fastener and in the middle of the fastener gap.

10. The special material according to claim 1, characterized in that, The nano-reinforcing filler is nano-silica; the special material is suitable for construction temperatures from -10℃ to 35℃; after curing, the special material forms an organic-inorganic composite structure with UV aging resistance ≥5000h and can withstand train dynamic load fatigue verification at frequencies of 5-20Hz and cycles ≥3 million times, without the risk of chipping or splashing; the total construction time of the method is ≤2 hours, which is suitable for the railway's 90-240 minute track maintenance window construction requirements, and the entire construction process does not require large equipment; through the regular transverse joint setting described in step 4, the large-area continuous repair layer is divided into independent plates, releasing temperature stress and shrinkage deformation, reducing the shear stress at the repair layer interface by more than 40%, and avoiding the generation of irregular cracks.

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