Method for improving surface wear resistance and corrosion resistance of seawater immersion concrete ditch

Abstract

This invention discloses a method for improving the wear and corrosion resistance of concrete trench surfaces immersed in seawater. A high-viscosity, high-consistency underwater non-dispersible putty with a yield stress ≥20 Pa and a viscosity of 5000-8000 mPa·s is used, composed of sulfoaluminate cement, silica fume, graded quartz sand, polymeric flocculant, and polycarboxylate superplasticizer. A specialized mold system is used, including an inflatable flexible sealing base, a rigid support frame, a bottom injection port, and a top venting and drainage channel. During construction, the mold is installed without drainage, and the putty is pumped in through the bottom injection port. The high viscosity and high yield stress of the putty create a plunger-like propulsion, completely expelling accumulated water and air through the top venting valve. After curing, a repair layer firmly bonded to the substrate is formed. This invention eliminates the need for cofferdam drainage, achieves a repair layer bond strength ≥1.5 MPa, an abrasion rate ≤1.0 kg / m², and improves construction efficiency by over 70%, making it suitable for rapid and durable repair of marine engineering trenches.

Description

Technical Field

[0001] This invention relates to a method for improving corrosion resistance, and more particularly to a method for improving the wear resistance and corrosion resistance of concrete ditch surfaces immersed in seawater. Background Technology

[0002] Seawater-soaked concrete drainage ditches are widely used in the drainage systems of coastal ports, docks, desalination plants, and coastal power plants. These ditches are subjected to prolonged immersion and scouring by seawater, causing severe corrosion and abrasion on their concrete surfaces. The approximately 3.5% salinity of seawater, along with corrosive media such as chloride, sulfate, and magnesium ions, continuously penetrates the concrete surface, causing steel reinforcement corrosion and concrete expansion and cracking. Simultaneously, the sand and suspended solids carried by the water flow abrade the ditch bottom and sidewalls, exposing aggregates and causing surface erosion, forming grooves and pits, further accelerating the erosion by corrosive media. Therefore, effective wear-resistant and corrosion-resistant protection and repair of the concrete ditch surface are crucial for ensuring the long-term stable operation of marine engineering facilities.

[0003] Currently, the following technical approaches are mainly used for the repair of concrete ditches soaked in seawater:

[0004] 1. Cofferdam Drainage Dry Repair Method: This method involves constructing a temporary cofferdam or caisson to pump out accumulated water from the ditch, creating a dry environment. Then, polymer-modified cement mortar, epoxy mortar, or glass flake putty is applied to the surface for repair by scraping or spraying. This method offers easy quality control and produces a high-density repair layer. However, the cofferdam construction cost is high, drainage operations are time-consuming, and it requires interrupting the operation of continuously running drainage systems, severely impacting facility availability.

[0005] 2. Underwater Non-Dispersible Mortar Spraying Method: This method uses specialized underwater spraying equipment to directly spray cement-based mortar mixed with an anti-dispersant agent onto the underwater concrete surface. While this method eliminates the need for drainage, the cement slurry is easily washed away by water flow during the spraying process, resulting in high surface sand content and uneven strength. Furthermore, moisture easily remains between the repair layer and the substrate, and the bond strength is typically less than 50% of that achieved with dry application, making it difficult to withstand subsequent water erosion.

[0006] 3. Epoxy grouting and topcoat: Underwater epoxy grout is used to cover the defective areas through injection pipes or manual application. Epoxy materials have high bonding strength and excellent chemical corrosion resistance, but they are expensive, have a short application window (usually only 30-60 minutes), require extremely clean substrates, and are prone to defects such as air bubbles and hollow areas in large-area trench repairs.

[0007] 4. Permeable Bag Concrete Method: Premixed concrete is filled into permeable bags, which are then laid and secured underwater by divers. This method is suitable for large-volume fillings, but it is difficult to control the thickness for thin surface repairs (typically requiring 10-30mm), and gaps easily form between the bags and the trench walls, making it difficult to guarantee compaction.

[0008] 5. Water-based pipeline repair method: For example, existing patent literature (CN201310266304.1) discloses a water-based pipeline repair method, which involves installing a diversion channel to guide the water flow in the ditch, and then injecting repair material between the diversion channel and the pipe wall. Although this method avoids complete cofferdam drainage, it still requires changing the original water flow path, making it poorly applicable to high-flow-rate ditches. Furthermore, the installation of the diversion channel is complex and cannot achieve thin-layer uniform repair.

[0009] However, the aforementioned existing technical solutions still have the following objective technical defects in practical applications:

[0010] The conflict between drainage and operational efficiency: While cofferdam drainage can ensure construction quality, it faces problems such as long construction periods, complex temporary structures, and significant interference with operational facilities, making it unsuitable for existing ditches requiring rapid repair. Non-drainage-free construction (such as underwater spraying and water-based pipe repair methods) saves time, but issues with material dispersion and interface adhesion are prominent, making it difficult to balance efficiency and quality.

[0011] Interface treatment is difficult: In underwater environments, biofilms, loose sediments, and corrosion products adhere to the concrete surface, which are difficult to completely remove with existing technologies, resulting in a weak bond between the repair layer and the substrate. In particular, common side or top opening grouting methods (including the grouting methods mentioned above for repairing pipes and canals with water) have a concrete mixture density that is only slightly higher than water, making it impossible to effectively drain accumulated water and loose sediments from the trench. This easily leads to the formation of water pockets at the bottom of the trench, and water films and weak interlayers easily form at the interface between the old and new layers, causing the repair layer to peel off and delaminate, which seriously affects the bond strength and long-term durability between the repair layer and the substrate.

[0012] Insufficient material adaptability: Conventional underwater non-dispersible concrete has a slump controlled at 180-220mm, which is highly fluid but lacks viscosity. It is prone to segregation in narrow ditches, and the sinking of coarse aggregates leads to a decrease in surface abrasion resistance. While epoxy materials have adjustable viscosity, they are brittle, have limited impact and abrasion resistance, and are sensitive to damp substrates, making it difficult to meet the dual requirements of abrasion resistance and corrosion resistance at the same time.

[0013] Construction quality control is difficult: underwater visibility is poor, and traditional side or top grouting cannot accurately determine the density of the repair layer, which can easily lead to defects such as honeycomb and holes; moreover, the repair thickness is difficult to control evenly, and local areas that are too thin are prone to premature failure, resulting in a decline in overall protective performance.

[0014] Therefore, it is necessary to provide a method for improving the surface wear and corrosion resistance of concrete ditches used in seawater immersion that can overcome one or more of the above-mentioned defects. Summary of the Invention

[0015] To address the shortcomings of existing technologies, this invention discloses a high-viscosity, high-consistency, underwater-non-dispersible putty, the technical solution of which is as follows:

[0016] A high-viscosity, high-consistency underwater non-dispersible putty, characterized in that the putty has a yield stress ≥20 Pa and a viscosity of 5000-8000 mPa·s; by weight, its components include: 60-70 parts of sulfoaluminate cement, 5-10 parts of silica fume, 20-30 parts of graded quartz sand with a particle size of 0.1-1.0 mm, 0.8-1.2 parts of polymeric flocculant, 0.5-1.0 parts of polycarboxylate superplasticizer, and a water-cement ratio of 0.25-0.30, wherein the cementing material is the sum of sulfoaluminate cement and silica fume.

[0017] This invention also discloses a mold system for repairing concrete ditches soaked in seawater, characterized in that the mold system is used in conjunction with the aforementioned high-viscosity, high-consistency underwater non-dispersible putty, comprising:

[0018] A flexible sealing base, which is an inflatable rubber sealing strip or a polyurethane foam sealing gasket, is arranged along the junction of the bottom plate and the side wall of the ditch. The inflatable rubber sealing strip forms a watertight barrier by inflation, and the polyurethane foam sealing gasket forms a watertight barrier by compression and deformation.

[0019] The rigid support frame, assembled from lightweight aluminum alloy or fiberglass profiles, spans both sides of the trench, providing vertical support and template positioning. The frame spacing is 1.0-1.5m. The frame is equipped with adjusting bolts or spiral jacks to adjust the distance between the sealing base and the bottom and sidewalls of the trench, thereby controlling the repair layer thickness to be adjustable within the range of 10-50 mm.

[0020] The bottom injection port, located at the lowest point of the mold, is a one-way valve injection port used to connect to the delivery pump pipe;

[0021] The top venting and drainage channel is located at the highest point of the mold and is an openable venting valve with a connecting hose extending out of the trench.

[0022] This invention also discloses a method for improving the wear resistance and corrosion resistance of concrete ditch surfaces immersed in seawater, characterized by using the aforementioned high-viscosity, high-consistency underwater non-dispersible putty and the aforementioned mold system, including the following steps:

[0023] Pretreatment of the base surface: High-pressure water jet is used to flush the trench walls and bottom to remove the biofilm and loose corrosion products, exposing the aggregate to form a rough interface; at the same time, the bottom silt is pumped out to keep the section to be repaired clean.

[0024] Mold installation and positioning: The segmented molds are lowered into the water and spliced ​​sequentially along the longitudinal direction of the ditch. The sealing base is made to fit tightly against the bottom and side wall of the ditch by adjusting the frame bolts. If an inflatable rubber sealing strip is used, it is inflated to 0.1~0.15 MPa to ensure water tightness. If a polyurethane foam sealing gasket is used, it is compressed and deformed to a compression rate of ≥30% to form a watertight barrier. The top venting channel is also checked to ensure it is unobstructed.

[0025] Material grouting: A piston-type grouting pump is used to pump the mixed high-viscosity putty into the bottom grouting port. The material forms a plunger-like propulsion in the mold cavity, pushing the accumulated water upwards and draining it out of the trench through the top vent valve. The grouting speed is controlled at 5-10 L / min, and the grouting pressure is 0.2-0.4 MPa. Observe the water discharge from the vent valve. When the discharged liquid changes from accumulated water to viscous slurry, close the vent valve and maintain the pressure for 2-3 minutes.

[0026] Curing and Demolding: After the material has initially set underwater, slowly release the pressure, remove the mold support, and remove the sealing base;

[0027] Segmented continuous construction: After each segment is repaired, the mold is moved forward, with an overlap length of not less than 200mm. A handheld vibrator is used to assist in compaction at the overlap.

[0028] Beneficial effects

[0029] 1. Significantly Improved Interface Bonding Performance: Through a bottom-water injection process, utilizing the plunger-like propulsion characteristics of high-viscosity putty, accumulated water and loose deposits within the mold are completely expelled from the repair area, thoroughly eliminating the water film and weak interlayer between the old and new interfaces. The 7-day underwater bond strength between the repair layer and the saturated, dry concrete substrate can reach over 1.5 MPa, which is more than 100% higher than the traditional underwater non-dispersible mortar spraying method (typically 0.5–0.8 MPa), reaching or even exceeding the bonding level of dry construction methods, effectively preventing peeling and detachment of the repair layer.

[0030] 2. Excellent wear and corrosion resistance of the repair layer: Utilizing a composite cementitious system of sulfoaluminate cement and silica fume, combined with graded quartz sand and optional steel fibers, the repair layer exhibits high density (apparent porosity ≤5%) and low abrasion rate. Underwater steel ball testing shows an abrasion rate ≤1.0 kg / m², which can be further reduced to below 0.6 kg / m² after adding steel fibers. Simultaneously, the micro-expansion characteristics of sulfoaluminate cement and the pozzolanic effect of silica fume jointly enhance resistance to chloride and sulfate ion penetration, resulting in significantly superior durability compared to conventional repair materials.

[0031] 3. Significantly improved construction efficiency, no need for drainage or operation interruption: This invention does not require the construction of cofferdams, the pumping out of accumulated water in the ditch, or changes to the original water flow path. The repair of a single 2-3 m section of the ditch (including mold installation, grouting, curing, and demolding) can be completed within 8-12 hours. Compared with the traditional cofferdam drainage dry repair method (which usually takes more than 30 hours), it shortens the construction period by more than 70% and does not interrupt the continuous operation of the drainage system. It is particularly suitable for active marine engineering facilities that require rapid repair.

[0032] 4. Highly controllable construction quality: Through the combination of the rigid frame of the mold system and the flexible sealing base, the thickness of the repair layer can be precisely adjusted within the range of 10-50mm as needed, and the flatness can reach 3mm / 2m. The top venting channel ensures that air and water inside the mold are completely discharged, and the repair layer is free of defects such as honeycomb, holes, and hollow areas, resulting in uniform and reliable quality.

[0033] 5. Excellent economic and environmental performance: The cement-based putty material used in this invention reduces the cost by more than 50% compared to underwater epoxy grouting materials, and the mold system can be reused more than 50 times, significantly reducing the overall repair cost. Furthermore, the material does not contain chlorides or other corrosion promoters, posing no risk of rust to reinforcing steel, and underwater construction does not generate pollution emissions, making it environmentally friendly.

[0034] 6. Strong environmental adaptability: This method is generally applicable to seawater trenches with flow velocities ≤0.5m / s. When the flow velocity is between 0.5m / s and 0.8m / s, effective construction can be achieved by adding temporary baffles to the outside of the mold system. Flexible rubber sealing strips should be installed at the contact points between the baffles and the trench wall to prevent lateral water flow from damaging the mold seal. When the flow velocity s>0.8m / s, it is recommended to take temporary diversion measures to reduce the flow velocity in the repair section to below 0.5m / s before proceeding with construction. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the installation cross-section of the mold system of the present invention. Detailed Implementation

[0036] Example 1: High-viscosity, high-consistency underwater non-dispersible putty

[0037] To address the issue that existing underwater repair materials cannot simultaneously meet the requirements of high bonding strength, high anti-dispersion properties, high abrasion resistance, and rheological properties suitable for top-water injection, this invention provides a cement-based thixotropic putty with a specific composition, exhibiting a yield stress ≥20 Pa, viscosity 5000~8000 mPa·s, water-to-land strength ratio ≥75%, 7-day bond strength ≥1.5 MPa, and abrasion rate ≤1.0 kg / m².

[0038] 1. Composition and weight of putty

[0039] By weight, this putty consists of the following essential components:

[0040] Sulfoaluminate cement: 60-70 parts

[0041] Silica fume: 5-10 parts

[0042] Graded quartz sand (particle size 0.1~1.0mm): 20~30 parts

[0043] Polymer flocculant: 0.8–1.2 parts

[0044] Polycarboxylate superplasticizer: 0.5–1.0 parts

[0045] Water-cement ratio (mass ratio of water to cementitious materials, i.e., cement + silica fume): 0.25~0.30.

[0046] For high-scouring areas, steel fibers can be added at a ratio of 1% to 3% of the total weight of the dry powder (cement + silica fume + quartz sand + flocculant + water-reducing agent).

[0047] 2. Functions and roles of each component, selection criteria, and reasons for scope limitations

[0048] 2.1 Sulfoaluminate cement (60-70 parts)

[0049] Functions and uses:

[0050] Sulfoaluminate cement, as the main cementitious material, provides the following key functions: (1) Early strength: The hydration reaction is fast, the initial setting time underwater is 4-6 hours, and the strength can reach 60% of the design strength 12 hours after final setting, meeting the requirements of rapid demolding and continuous construction; (2) Micro-expansion: Hydration generates ettringite (AFt), which produces micro-expansion in volume, compensating for the shrinkage of cement stone and enhancing the bonding with the old concrete matrix; (3) Resistance to seawater corrosion: High concentration of SO4 in seawater 2- (Approximately 2700 mg / L) poses a serious risk of corrosion to ordinary silicate cement, while the Ca, Al, and S minerals in sulfoaluminate cement react with gypsum to generate AFt, leaving very little aluminate phase and exhibiting excellent sulfate resistance; (4) Synergistic effect with silica fume: silica fume provides active SiO2, which reacts with Ca(OH)2 generated during the hydration of sulfoaluminate cement to generate CSH gel, while promoting the formation of AFt and densifying the interfacial transition zone.

[0051] Reasons for material selection:

[0052] Compared to ordinary Portland cement (PO 42.5), it has slower hydration (underwater initial setting >10h) and larger shrinkage (drying shrinkage approximately 400×10⁻⁶). -6With a sulfate resistance coefficient below 0.8, it cannot maintain its bond strength in a seawater environment for a long time. In contrast, the 28-day expansion rate of sulfoaluminate cement can be controlled within 0.05% to 0.10%, which is beneficial for underwater bonding.

[0053] Reason for scope limitation:

[0054] Less than 60 parts: Insufficient cementitious material, the yield stress of the slurry drops to <20Pa (the actual measured yield stress is only 12Pa when the cement content is 50 parts), and the 7-day bond strength is <1.5MPa (the actual measured strength is 1.1MPa); at the same time, the heat of hydration of cement is reduced, the early strength is insufficient, and it is impossible to reach 60% of the design strength within 12 hours, which affects the demolding time.

[0055] For quantities exceeding 70 parts: the slurry viscosity is too high (>8000mPa·s), the slump expansion is <180mm, and the pump pressure needs to be increased (>0.5MPa) during grouting, which can easily lead to mold seal failure; moreover, the cost increases significantly and the economy is poor.

[0056] Critical evidence: With other components fixed, the cement content is positively correlated with yield stress (r=0.96) and negatively correlated with slump spread (r=-0.93). 60-70 parts is the balance range that takes into account both rheology and strength.

[0057] 2.2 Silica fume (5-10 parts)

[0058] Functions and uses:

[0059] Silica fume (average particle size 0.1–0.3 μm, specific surface area 15–25 m²) 2 / g) as an active filler, plays the following roles: (1) Physical filling: fills the gaps between cement particles (average particle size 15-30μm), increases the density of the paste, and reduces the porosity to below 5%; (2) Increases yield stress: high specific surface area particles form a thixotropic network through van der Waals forces and flocculant bridging, increasing the yield stress from 9Pa without silica fume to more than 20Pa; (3) Volcanic ash reaction: consumes Ca(OH)2 to generate CSH gel, improving the chemical bond strength with old concrete; (4) Anti-dispersion: the surface of silica fume particles is negatively charged, adsorbs flocculant molecules, and enhances the underwater scouring resistance.

[0060] Reasons for material selection:

[0061] Compared to fly ash (particle size 10–30 μm) or slag powder (particle size 5–20 μm), its filling effect and pozzolanic activity are far lower than those of silica fume. Experiments show that replacing an equal amount of silica fume with fly ash reduces the yield stress to 13 Pa and the water-to-land strength ratio to 68%. Silica fume is an irreplaceable key component.

[0062] Reason for scope limitation:

[0063] Less than 5 parts: the yield stress usually drops to below 15 Pa, the water-to-land strength ratio is <75% (the water-to-land strength ratio is 72% when the actual measurement is 3 parts silica fume), the bond strength is <1.2 MPa; and the bleeding rate of the slurry increases, and slight segregation occurs when falling into water.

[0064] For amounts exceeding 10 parts: an additional amount of water-reducing agent (>1.2 parts) is required to maintain fluidity, and the slurry viscosity is too high (>10000mPa·s), making it difficult for air bubbles to escape through the top vent valve, easily forming honeycomb pores; at the same time, the cost increases significantly.

[0065] Critical evidence: The silica fume content has a logarithmic relationship with the yield stress. The content of 5 to 10 parts is in a rapid increase plateau region, and the increase slows down when the content exceeds 10 parts, but the viscosity increases sharply.

[0066] 2.3 Graded quartz sand (particle size 0.1-1.0 mm, 20-30 parts)

[0067] Functions and uses:

[0068] Quartz sand, as a wear-resistant aggregate, provides the following key functions: (1) Wear-resistant skeleton: Quartz has a Mohs hardness of 7, which is much higher than that of ordinary river sand (hardness 5-6). In the underwater steel ball abrasion test, the abrasion rate of the quartz sand system is ≤1.0kg / m 2 The river sand system has a density of ≥1.8 kg / m³. 2 (2) Gradation filling: 0.1~1.0mm continuous gradation forms a “bimodal” packing system with silica fume, with the densest packing porosity <15%, reducing the amount of cement paste used; (3) Controlling shrinkage: Aggregate constrains the shrinkage of cement stone, reducing microcracks.

[0069] Reasons for material selection:

[0070] Coarse aggregate (>2mm) is not used because the repair layer thickness is only 10-50mm, and coarse aggregate is prone to causing grout blockage and poor surface smoothness. Fine sand (<0.1mm) is not used because its specific surface area is too large, requiring increased water consumption and reducing strength and anti-dispersion properties. Sieve tests show that a 0.1-1.0mm gradation has the lowest porosity with a fineness modulus of 2.3-2.6.

[0071] Reason for scope limitation:

[0072] Less than 20 parts: Insufficient aggregate, abrasion rate > 1.0 kg / m² (actually measured abrasion rate of 1.45 kg / m² at 15 parts). 2 Furthermore, the slurry shrinks more, making it prone to drying shrinkage cracks.

[0073] More than 30 parts: Excessive aggregate leads to decreased slurry fluidity, slump expansion <180mm, and voids are easily formed at the corners during grouting; at the same time, the yield stress increases to more than 30Pa, requiring higher pump pressure.

[0074] Critical evidence: The amount of quartz sand is negatively correlated with the abrasion rate (r=-0.94) and negatively correlated with the slump spread (r=-0.91). 20-30 parts is the optimal balance between abrasion resistance and workability.

[0075] 2.4 Polymer flocculant (0.8–1.2 parts)

[0076] Functions and uses:

[0077] The polymeric flocculant (preferably anionic polyacrylamide, molecular weight 8 million to 12 million) achieves underwater anti-dispersion and top-water-coagulation capabilities through the following mechanisms: (1) Bridging flocculation: Long-chain polymers adsorb multiple cement particles to form a three-dimensional network structure, which keeps the slurry intact in water and has an anti-dispersion index (water-land strength ratio) ≥75%; (2) Viscosity enhancement: Increases the slurry viscosity to 5000 to 8000 mPa·s, so that a stable slurry-water interface is formed during top-water injection, avoiding cross-flow mixing; (3) Thixotropy: High yield stress (≥20 Pa) at rest, and viscosity decreases under pump shear, which facilitates injection.

[0078] Reasons for material selection:

[0079] In conventional underwater non-dispersible concrete, the flocculant dosage is only 0.2-0.5%, mainly used to prevent segregation, which cannot achieve the high viscosity required for top-water dispersibility. Comparative tests show that at a dosage of 0.5%, the viscosity is only 2800 mPa·s, the slurry-water interface is unstable, and accumulated water cannot be completely expelled. This invention increases the dosage to 0.8-1.2%, giving the slurry a "plunger-like propulsion" capability.

[0080] Reason for scope limitation:

[0081] Less than 0.8 parts: viscosity <5000mPa·s, during top water injection, turbulent mixing occurs at the interface between the grout and the accumulated water, the accumulated water cannot be completely discharged, a water film remains at the interface, and the 7-day bond strength drops to below 1.0MPa (measured 0.8MPa); water-to-land strength ratio <70%.

[0082] Higher than 1.2 parts: viscosity > 10000 mPa·s, pumping pressure > 0.5 MPa, which can easily lead to mold seal leakage; and air bubbles inside the slurry are difficult to escape through the top exhaust valve, resulting in honeycomb-like pores in the repair layer.

[0083] Criticality evidence: The flocculant dosage is exponentially related to viscosity, and 0.8 to 1.2 parts are within the ideal window of 5000 to 8000 mPa·s.

[0084] 2.5 Polycarboxylate superplasticizer (0.5-1.0 parts)

[0085] Functions and uses:

[0086] Polycarboxylate superplasticizer (solid content 40%, water reduction rate ≥30%) provides initial fluidity at low water-cement ratio (0.25~0.30): (1) Disperses cement particles: releases encapsulated water through steric hindrance, so that the slump expansion of the slurry reaches 180~220mm; (2) Adjusts rheological curve: forms competitive adsorption with flocculant, so that the slurry still maintains sufficient viscosity after shear thinning, avoiding segregation; (3) Delays hydration: appropriately prolongs the initial setting time to ensure the grouting window period.

[0087] Reasons for material selection:

[0088] Naphthalene-based or aliphatic water-reducing agents have poor compatibility with polymeric flocculants, easily leading to flocculant precipitation and loss of anti-dispersibility. Polycarboxylate water-reducing agents, with their comb-like molecular structure, work synergistically with flocculants, providing flowability without disrupting the flocculation network.

[0089] Reason for scope limitation:

[0090] Less than 0.5 parts: The initial fluidity of the slurry is insufficient, and the slump spread is <180mm. The water-cement ratio needs to be increased to >0.30 for grouting. However, after the water-cement ratio is increased, the water-to-land strength ratio drops to <70%, and the bond strength is <1.2MPa.

[0091] Above 1.0 part: Excessive dispersion destroys the flocculated bridging network, the yield stress drops to <15Pa, segregation occurs when falling into water, and the water-to-land strength ratio is <75%.

[0092] Critical evidence: The dosage of water-reducing agent is positively correlated with slump expansion and negatively correlated with yield stress, with 0.5 to 1.0 parts being the equilibrium point.

[0093] 2.6 Water-to-binder ratio (0.25-0.30)

[0094] Function and role: The water-cement ratio is the core parameter for controlling the performance of the paste, and it directly affects the strength, viscosity and anti-dispersion properties.

[0095] Reason for scope limitation:

[0096] Below 0.25: Even with sufficient water-reducing agent, the slump spread is still <180mm, making pumping impossible; and the cement hydration is insufficient, resulting in a decline in strength later on.

[0097] Above 0.30: Excessive free water dilutes the flocculated network, resulting in a yield stress <15Pa, a water-to-land strength ratio <75%, and a bond strength <1.2MPa.

[0098] Critical evidence: For every 0.01 increase in the water-cement ratio, the yield stress decreases by approximately 1.5 Pa, and the water-to-land strength ratio decreases by approximately 1.8%.

[0099] 3. Mechanism and necessity justification of synergistic effects among components

[0100] The reason why this invention contains only the above five essential components (excluding water and optional steel fibers) is based on the following synergistic mechanism: the target performance cannot be achieved if any additional component is added or missing.

[0101] 3.1 The four essential components form a "quadrivalent synergistic" system

[0102] Cement (sulfoaluminate) + silica fume: forms a highly active cementitious system. Cement provides calcium. 2+ Al 3+ Silica fume provides active SiO2, which hydrates to produce CSH and AFt, giving the slurry its micro-expansion and high bonding strength. Without silica fume, only cement hydration produces Ca(OH)2, resulting in a loose interfacial zone and a decrease in bonding strength of more than 50%.

[0103] Flocculant + Water-reducing agent: This forms a "competitive adsorption-dynamic equilibrium" rheological regulation mechanism. The water-reducing agent preferentially adsorbs onto the surface of cement particles, providing initial dispersion; the flocculant forms a network through long-chain bridging. When both coexist, the slurry has high viscosity under low shear and can be pumped under high shear. Without the water-reducing agent, the slurry cannot flow; without the water-reducing agent, the slurry segregates in water.

[0104] Quartz sand + silica fume: forms a "bimodal gradation" for the densest packing. Silica fume fills the voids in the quartz sand, increasing the density of the slurry while reducing the amount of cement paste needed, thus lowering costs. Without silica fume, more cement is required to fill the voids between the sand particles, and wear resistance decreases.

[0105] Flocculant + Silica Fume: The high specific surface area of ​​silica fume enhances flocculant adsorption, synergistically increasing yield stress. Without silica fume, the flocculant mainly adsorbs onto cement particles, resulting in insufficient network strength and a yield stress <15Pa.

[0106] 3.2 Effect verification of the absence of any component (comparative example)

[0107]

[0108] 3.3 Negative impacts of adding additional components

[0109]

[0110] Therefore, the components and their dosage ranges of the present invention are the "minimum necessary set" determined through extensive experimental screening, and are unique and cannot be simplified.

[0111] 4. Detailed performance data of specific embodiments and comparative examples

[0112] 4.1 Example 1-1 (Benchmark formulation, median ratio)

[0113] Composition (parts by weight):

[0114] Sulfoaluminate cement: 65 parts (actual batch size 65kg)

[0115] Silica fume: 8 parts (8 kg)

[0116] Graded quartz sand (0.1~1.0mm): 25 parts (25kg)

[0117] Polymer flocculant: 1.0 part (1.0 kg)

[0118] Polycarboxylate superplasticizer: 0.7 parts (0.7 kg)

[0119] Water: Cementitious material (65+8=73kg) × 0.27 = 19.71kg

[0120] Preparation method: Using a forced mixer, first mix and disperse the powdered polymer flocculant with the mixing water (or stir until dissolved), and then put it into the mixer; then add cement, silica fume, quartz sand, and water-reducing agent, and continue to stir for 3 minutes until uniform and free of lumps.

[0121] Fresh mix performance:

[0122] Collapse spread: 205mm (GB / T 50080)

[0123] Yield stress: 23 Pa (Brookfield RST rheometer, Vane rotor)

[0124] Viscosity: 6600 mPa·s (Brookfield DV2T, LV-62 rotor, 25℃, 20 rpm)

[0125] Hardening performance (cured in seawater at 20℃):

[0126] Water-to-land intensity ratio (7d): 83% (DL / T 5117)

[0127] Bond strength (7 days, compared with saturated surface-dry concrete): 1.72 MPa (GB / T 50081 pull-out method)

[0128] Abrasion rate (underwater steel ball method): 0.82 kg / m² (DL / T 5150)

[0129] Initial setting time: 5.2 hours

[0130] Strength after 12 hours of final setting: 64% of design strength

[0131] Conclusion: All indicators are better than the required values, and the overall performance is the best.

[0132] 4.2 Examples 1-2 (Lower Limit Formulation)

[0133] composition:

[0134] Sulfoaluminate cement: 60kg

[0135] Silica fume: 5kg

[0136] Quartz sand: 20kg

[0137] Flocculant: 0.8 kg

[0138] Water-reducing agent: 0.5kg

[0139] Water: 65kg × 0.25 = 16.25kg of cementitious material

[0140] performance:

[0141] Collapse spread: 218mm

[0142] Yield stress: 21 Pa

[0143] Viscosity: 5100 mPa·s

[0144] Water-to-land intensity ratio: 76%

[0145] Bond strength: 1.53 MPa

[0146] Abrasion rate: 0.98 kg / m 2

[0147] Initial setting time: 4.8 hours

[0148] Conclusion: All indicators reached the lower limit, and the economy was optimal, but the construction window was short (about 30 minutes), making it suitable for small-area rapid repairs.

[0149] 4.3 Examples 1-3 (High-limit formulation, steel fiber added)

[0150] composition:

[0151] Sulfoaluminate cement: 70kg

[0152] Silica fume: 10kg

[0153] Quartz sand: 30kg

[0154] Flocculant: 1.2 kg

[0155] Water-reducing agent: 1.0 kg

[0156] Steel fiber (8mm in length, 0.25mm in diameter): Its dosage accounts for 2% of the total weight of sulfoaluminate cement, silica fume, and graded quartz sand. In this embodiment, the total weight of the three components is 70 + 10 + 30 = 110kg, so the steel fiber dosage is 110kg × 2% = 2.2kg;

[0157] Water: 80kg × 0.30 = 24.0kg of cementitious material

[0158] performance:

[0159] Collapse spread: 188mm

[0160] Yield stress: 28 Pa

[0161] Viscosity: 7800 mPa·s

[0162] Water-to-land intensity ratio: 86%

[0163] Bond strength: 1.85 MPa

[0164] Abrasion rate: 0.58 kg / m 2

[0165] Initial setting time: 5.8 hours

[0166] Conclusion: The bonding strength and abrasion resistance are significantly improved, making it suitable for high-scouring areas, but the cost is slightly higher.

[0167] 4.4 Comparative Example 1 (no silica fume, conventional flocculant dosage)

[0168] composition:

[0169] Sulfoaluminate cement: 73kg (replaces silica fume)

[0170] Silica fume: 0

[0171] Quartz sand: 25kg

[0172] Flocculant: 0.5 kg

[0173] Water-reducing agent: 0.5kg

[0174] Water: Water-to-binder ratio 0.35 (to improve fluidity due to the absence of silica fume), cementitious material 73kg, water = 25.55kg

[0175] performance:

[0176] Collapse spread: 230mm

[0177] Yield stress: 9 Pa

[0178] Viscosity: 2800 mPa·s

[0179] Water-to-land intensity ratio: 58%

[0180] Bond strength: 0.7 MPa

[0181] Abrasion rate: 1.35 kg / m 2

[0182] Conclusion: It does not meet the requirements of this invention and cannot be used for bottom top water injection.

[0183] 4.5 Comparative Example 2 (without flocculant)

[0184] Composition: Same as in Example 1-1, but with 0% flocculant.

[0185] performance:

[0186] Collapse spread: 225mm

[0187] Yield stress: 6 Pa

[0188] Viscosity: 1200 mPa·s

[0189] Water-to-land strength ratio: 35% (substance formed in water completely disintegrates).

[0190] Bond strength: 0.3 MPa (interfacial water film cannot be discharged)

[0191] Abrasion rate: 1.80 kg / m 2

[0192] Conclusion: Completely lost its ability to resist underwater dispersion.

[0193] 4.6 Comparative Example 3 (water-to-binder ratio 0.35)

[0194] Composition: Same as Example 1-1, but the water-to-binder ratio is increased to 0.35.

[0195] performance:

[0196] Collapse spread: 235mm

[0197] Yield stress: 11 Pa

[0198] Viscosity: 3800 mPa·s

[0199] Water-to-land intensity ratio: 62%

[0200] Bond strength: 0.9 MPa

[0201] Abrasion rate: 1.20 kg / m 2

[0202] Conclusion: The water-cement ratio exceeded the upper limit, and the key indicators failed to meet the standards.

[0203] The high-viscosity, high-consistency underwater non-dispersible putty provided by this invention achieves high yield stress (≥20Pa), high viscosity (5000~8000mPa·s), high water-to-land strength ratio (≥75%), high bond strength (≥1.5MPa), and low abrasion rate (≤1.0kg / m³) through a specific combination and precise proportion of sulfoaluminate cement, silica fume, graded quartz sand, polymeric flocculant, and polycarboxylate superplasticizer, utilizing a quaternary synergistic mechanism (gelling-filling-flocculation-dispersion). 2 The comprehensive performance of the putty is crucial. Each component is indispensable, and their dosage range has strict critical limits; adding other components (such as fly ash, expanding agent, defoamer, coarse aggregate, etc.) will disrupt the synergistic balance, leading to a decline in performance. Examples 1-1 to 1-3 above all meet the requirements of this invention, while the comparative examples cannot. This putty, combined with a bottom-water-injection process, can completely drain interfacial water without requiring additional drainage, forming a dense repair layer with high adhesion and high wear resistance. This solves the technical problem that existing underwater repair materials cannot simultaneously achieve anti-dispersion, bonding strength, and wear resistance.

[0204] Example 2: Mold system for repairing concrete ditches soaked in seawater

[0205] Existing underwater repair molds cannot adapt to narrow trenches, cannot form a sealed cavity under water conditions, and cannot be used in conjunction with bottom top water injection processes. This invention provides a quick-installation, reusable adaptive sealing mold system. Its design parameters (such as injection port location, venting channel, sealing pressure, etc.) are optimized for the rheological properties of the putty described in Example 1 (viscosity 5000-8000 mPa·s, yield stress ≥20 Pa). It can form a watertight cavity with the inner wall of the trench without drainage, providing a process carrier for bottom top water injection of this specific putty, while simultaneously achieving precise control of the repair layer thickness and orderly drainage of air bubbles and accumulated water. The mold system is installed inside the trench, with a flexible sealing base arranged along the junction of the trench bottom plate and sidewalls, and a rigid support frame spanning both sides of the trench and fixed by adjusting bolts. The bottom injection port is located at the lowest point of the mold and connected to the grouting pump via a delivery pump pipe; the top venting and drainage channel is located at the highest point of the mold and extends to above the water surface outside the trench via an venting hose; the repair layer fills the space between the inner cavity of the mold and the old concrete.

[0206] like Figure 1 As shown, the mold system is installed in the ditch, with the flexible sealing base arranged along the junction of the bottom plate and side wall of the ditch, and the rigid support frame spanning both sides of the ditch and fixed by adjusting bolts; the bottom grouting interface is set at the lowest point of the mold and connected to the grouting pump through the delivery pump pipe; the top exhaust and drainage channel is set at the highest point of the mold and extends to the water surface outside the ditch through the exhaust hose; the repair layer is filled between the inner cavity of the mold and the old concrete.

[0207] 1. Composition and technical solution of the mold system

[0208] A mold system for repairing concrete ditches soaked in seawater, the mold system comprising:

[0209] Flexible sealing base: It adopts an inflatable rubber sealing strip or a polyurethane foam sealing gasket, which is arranged along the junction of the bottom plate and the side wall of the water ditch. After inflation, it forms a watertight barrier.

[0210] Rigid support frame: assembled from lightweight aluminum alloy or fiberglass profiles, spanning both sides of the trench, providing vertical support and template positioning, with a frame spacing of 1.0 to 1.5m;

[0211] Bottom injection port: Located at the lowest point of the mold, it is a one-way valve injection port used to connect to the delivery pump pipe. Its inner diameter is ≥25mm to allow the putty containing 0.1~1.0mm quartz sand as described in Example 1 to pass through smoothly.

[0212] Top venting and drainage channel: Located at the highest point of the mold, it is an openable venting valve with a connecting hose extending out of the trench.

[0213] The inflation pressure of the flexible sealing base is 0.1 to 0.15 MPa.

[0214] All parameters of this mold system (inlet size, sealing pressure, frame spacing) match the key performance indicators of the putty in Example 1 (yield stress ≥20Pa, viscosity 5000~8000mPa·s, slump spread 180~220mm). For example, high-viscosity putty requires a sufficiently large inlet diameter (≥25mm) to prevent clogging; high-yield-stress putty exerts significant pressure on the mold sidewalls during injection, requiring the sealing base inflation pressure to be no less than 0.1MPa; the thixotropic (shear-thinning) properties of the putty allow for pumping at an injection pressure of 0.2~0.4MPa, eliminating the need for excessively high sealing pressure. The functions and parameter limitations of the following components are all optimized based on the characteristics of the putty in Example 1.

[0215] 2. The function, material selection criteria, and parameter limitations of each component.

[0216] 2.1 Flexible sealing base (inflatable rubber sealing strip or polyurethane foam sealing gasket)

[0217] Functions and uses:

[0218] The core function of the flexible sealing base is to form a dynamic watertight seal with the uneven bottom and sidewalls of the old concrete trench under non-drainage conditions, preventing the high-viscosity putty described in Example 1 from leaking from the bottom under grouting pressure. Specifically, it includes: (1) adapting to uneven base surfaces: the surface of concrete trenches soaked in seawater for many years often has defects such as corrosion pits and exposed aggregates. The flexible material can undergo 10-30% compression deformation under air pressure to fill local depressions; (2) resisting grouting pressure: the yield stress of the putty in Example 1 is ≥20Pa. The pump pressure during grouting is 0.2-0.4MPa. After the sealing strip is inflated to 0.1-0.15MPa, the contact pressure is sufficient to resist the internal pressure and prevent the grout from leaking out; (3) easy to remove: the sealing strip automatically retracts after depressurization.

[0219] Reasons for material selection:

[0220] Inflatable rubber sealing strip: Made of ethylene propylene diene monomer (EPDM) rubber, resistant to seawater corrosion, with a hardness of 50-60 Shore A and an elongation at break ≥300%. After inflation, the expansion ratio is 1.5-2.0 times, which can adapt to the groove width variation of ±10%.

[0221] Polyurethane foam sealing gasket: closed-cell structure, density 0.3~0.5g / cm³ 3 The permanent compression deformation is ≤10%. During use, it is compressed via frame bolts, with a thickness direction compression rate ≥30% (i.e., the compressed thickness is ≤70% of the original thickness). The corresponding unit length compression force control range is 2.0~4.0kN / m. This compression force range ensures that the sealing gasket deforms sufficiently to fill the base surface depression, without causing local crushing of the old concrete or excessive deformation of the rigid frame due to excessive pressure. During construction, a compression rate of 30% is the main control indicator, and the compression force is used as the verification basis.

[0222] Reason for parameter limitations (inflation pressure 0.1~0.15MPa):

[0223] This pressure range was specifically designed for the rheological properties of the putty in Example 1. Tests show that:

[0224] Below 0.1MPa: When the injection pressure reaches 0.2MPa (the minimum pressure required for putty pumping), the sealing contact pressure is insufficient, and the leakage rate is about 15%.

[0225] Above 0.15MPa: Excessive expansion of the sealing strip will cause excessive stress on the old concrete, which may lead to peeling; at the same time, excessive sealing pressure will make mold installation difficult and is not compatible with the low shear flow characteristics of the putty (no higher pressure is required).

[0226] Critical evidence: An injection test was conducted using the putty from Example 1-1 (viscosity 6600 mPa·s). At an air pressure of 0.12 MPa, there was no leakage at an injection pressure of 0.3 MPa, and the resilience of the sealing strip remained good.

[0227] 2.2 Rigid support frame (lightweight aluminum alloy or fiberglass profile)

[0228] Functions and uses:

[0229] The rigid support frame provides the following key functions: (1) Template positioning and repair thickness control: By adjusting the bolts, the sealing base is made to fit tightly against the bottom of the trench, and the distance between the sealing base and the old concrete surface is controlled (i.e., the repair layer design thickness is 10-50mm). This thickness range matches the maximum aggregate particle size (1.0mm) of the putty in Example 1 (≥10 times the maximum aggregate particle size, ensuring dense filling); (2) Resistance to grouting pressure: The high yield stress (≥20Pa) of the putty in Example 1 makes the pressure on the inner wall of the mold higher than that of ordinary cement grout during grouting (measured up to 0.4MPa). The frame needs to provide sufficient bending stiffness; (3) Segmented connection: Multiple frame longitudinal connecting rods form a whole, forming a 2-3m repair segment.

[0230] Reasons for material selection:

[0231] Lightweight aluminum alloy (6061-T6): density 2.7 g / cm³ 3 It is lightweight in water, making it easy for divers to handle; its yield strength is ≥240MPa and its elastic modulus is 70GPa, meeting the stiffness requirements.

[0232] Frame spacing 1.0–1.5m: This spacing was optimized based on the flowability (slump spread 180–220mm) of the putty in Example 1. If the spacing is too large (>1.5m), the flow resistance of the putty between adjacent frames increases, easily leading to areas of incomplete filling; if the spacing is too small (<1.0m), the cost increases. CFD simulation shows that a 1.2m spacing results in a putty filling rate ≥99.5%.

[0233] 2.3 Bottom filling port (one-way valve)

[0234] Functions and uses:

[0235] The bottom injection port is a key component connecting the delivery pump pipe and the mold cavity, located at the lowest point of the mold. Its design is designed for the high viscosity and aggregate content of the putty in Example 1: (1) One-way flow: prevents putty backflow when injection is interrupted (the putty has high viscosity, and backflow will cause blockage); (2) Anti-blockage: the inner diameter of the channel is ≥25mm to ensure that putty containing 0.1~1.0mm quartz sand can pass through smoothly; (3) Quick connection: the snap-fit ​​interface is convenient for underwater operation.

[0236] Reasons for material selection:

[0237] The valve body is made of 316L stainless steel, which is resistant to seawater corrosion.

[0238] The valve core uses a diaphragm-type check valve, which is more suitable for high-viscosity fluids containing particles than ball valves and is less prone to jamming.

[0239] The inner diameter of the interface is 25mm. It is calculated based on the maximum aggregate particle size (1.0mm) and maximum viscosity (8000mPa·s) of the putty in Example 1: empirical formula D ≥3×d_max × (η / 1000)^{0.2}, where d_max=1.0mm, η=8000mPa·s. The calculated value is D≥22.5mm, and 25mm is taken as a safety margin.

[0240] Installation location: It must be set at the lowest point in the longitudinal direction of the mold. For sloping ditches (0.5-2%), the injection port should be located at the lower downstream end, using gravity to assist the putty in being pushed upwards.

[0241] 2.4 Top exhaust and drainage channel (openable exhaust valve)

[0242] Functions and uses:

[0243] The top venting and drainage channel is the core component for achieving "top water replacement". Its function is closely related to the high yield stress characteristics of the putty in Example 1: (1) Discharge of accumulated water and air: During injection, the seawater and air in the mold are pushed upward by the putty from the bottom and discharged through the top venting valve. Since the yield stress of the putty in Example 1 is ≥20Pa, its propulsion in water is "plunger-like" rather than dispersed mixing, so the accumulated water can be completely replaced without crossflow; (2) Observe the filling state: the injection is completed by the substance flowing out of the venting valve (first turbid water, then viscous slurry); (3) Pressure retention and compaction: After closing the venting valve, maintain the pressure for 2-3 minutes and use the thixotropy of the putty to compensate for shrinkage.

[0244] Reasons for material selection:

[0245] The valve body is made of UPVC or 316L stainless steel, which is corrosion resistant.

[0246] The inner diameter of the exhaust channel should be ≥15mm to avoid blockage by putty.

[0247] The connecting hose is made of transparent PVC pipe with an inner diameter of ≥15 mm, making it easy to observe from the ground.

[0248] Installation location: It must be set at the highest point in both the longitudinal and transverse directions of the mold. For the fluidity of the putty in Example 1 (slump expansion 180-220mm), if the height difference between local high points exceeds 50mm, the putty may not be able to fill by itself, so multiple air vents (spaced ≤1m) need to be installed.

[0249] 3. The synergistic working mechanism between the mold system and the putty in Example 1

[0250] The mold system of this invention and the putty of Example 1 have the following "equipment-material" synergistic relationship, and together they constitute the whole of the bottom top water injection technology solution:

[0251] 3.1 Rheological property matching

[0252] High yield stress (≥20Pa) ensures the putty is pushed forward as a whole within the mold, preventing fingering; the top vent valve of the mold ensures that accumulated water is completely expelled. If a low yield stress material (such as conventional mortar) is used, it will mix with accumulated water during the pushing process, and even with a vent valve, complete replacement cannot be achieved.

[0253] The high viscosity (5000~8000mPa·s) stabilizes the lateral pressure applied by the putty to the mold sealing base; the mold's inflation sealing pressure (0.1~0.15MPa) just balances this lateral pressure, preventing leakage without excessive compression.

[0254] 3.2 Particle size and channel matching

[0255] The maximum aggregate particle size in the putty is 1.0mm, and the inner diameter of the mold pouring port is ≥25mm (≥25 times the maximum particle size) to ensure no risk of clogging.

[0256] The putty has a slump expansion of 180-220mm, corresponding to a flow radius of about 1.0-1.5m. Therefore, the spacing between the mold frames is set to 1.0-1.5m to ensure that the putty can completely fill the area between adjacent frames.

[0257] 3.3 Curing Time Matching

[0258] In Example 1, the initial underwater setting time of the putty is 4-6 hours, and the strength reaches 60% of the design strength 12 hours after final setting. The demolding time of the mold system is set to 12 hours later, at which time the repair layer has sufficient self-supporting capacity, and demolding will not cause deformation or detachment.

[0259] 3.4 Verification Experiment

[0260] A field grouting test was conducted using the putty from Example 1-1 (viscosity 6600 mPa·s, yield stress 23 Pa) and the mold system from Example 2-1 (air pressure 0.12 MPa, frame spacing 1.2 m, grouting port inner diameter 25 mm). Results: At a grouting pressure of 0.3 MPa and a grouting speed of 8 L / min, the grout transitioned to a continuous slurry approximately 30 seconds after water exited the vent valve. Pressure was maintained for 2 minutes after closing the vent valve. Demolding was performed after 12 hours of curing. The designed repair layer thickness was 30 mm, but the actual measured thickness was 29.3–31.0 mm, with a bond strength of 1.68 MPa. No honeycomb or voids were observed. Comparative test: When the mold was used with conventional low-viscosity mortar (viscosity 1500 mPa·s), the slurry-water interface was unstable during grouting. After water exited the vent valve, the slurry never transitioned to a pure slurry (water was always mixed in). A continuous water film remained at the bottom of the repair layer after demolding, and the bond strength was only 0.6 MPa.

[0261] 4. Installation and usage steps of the mold system (in conjunction with the putty in Example 1)

[0262] Base surface pretreatment.

[0263] Mold installation and positioning: The segmented molds (each segment 2-3m long) are lowered into the water and spliced ​​sequentially along the longitudinal direction of the ditch; the sealing base is made to fit tightly against the bottom and sidewall of the ditch by adjusting the frame bolts, and the design thickness of the repair layer is controlled (10-50mm, matching the maximum aggregate particle size of the putty in Example 1).

[0264] Inflate and seal: Inflate the rubber sealing strip to 0.1-0.15 MPa and check its water tightness.

[0265] Connecting the pipeline: Connect the bottom grouting interface to the grouting pump pipe, and lead the top vent valve hose to the outside of the trench.

[0266] Material injection: A piston-type grouting pump is used to pump the high-viscosity putty mixed according to the proportions in Example 1 into the bottom injection port. The injection pressure is 0.2-0.4 MPa and the speed is 5-10 L / min. Observe the water discharge from the vent valve. When the discharged liquid changes from water to viscous slurry, close the vent valve and maintain the pressure for 2-3 minutes.

[0267] Curing and Demolding: After underwater curing for 12 hours (when the putty strength reaches more than 60% of the design strength), slowly release the pressure and air, remove the mold support, and remove the sealing base.

[0268] Segmented continuous construction: After each segment is repaired, the mold is moved forward, with an overlap length of not less than 200mm. A handheld vibrator is used to assist in compaction at the overlap.

[0269] 4. The effects and advantages of the mold system (in conjunction with putty properties)

[0270] Compared with existing technologies (cofferdams, diversion channels, conventional templates), the mold system of this invention, when used in conjunction with the putty of Example 1, has the following unique advantages:

[0271]

[0272] 5. Specific Implementation Examples (Examples of mold system parameters, in conjunction with putty in Example 1)

[0273] Example 2-1 (Standard type, used with putty from Example 1-1)

[0274] Mold parameters:

[0275] Suitable for drainage ditches: 500mm wide, 600mm high, rectangular

[0276] Flexible sealing base: EPDM inflatable rubber strip, 30mm×20mm, inflation pressure 0.12MPa

[0277] Rigid support frame: 6061-T6 aluminum alloy, frame spacing 1.2m

[0278] Bottom filling port: 316L stainless steel diaphragm check valve, inner diameter 25mm

[0279] Top vent valve: UPVC ball valve, 15mm diameter, 2 valves installed (1.2m apart).

[0280] Putty preparation: Example 1-1 Putty (65kg cement, 8kg silica fume, 25kg quartz sand, 1.0kg flocculant, 0.7kg water-reducing agent, 19.71kg water)

[0281] Injection results: Injection pressure 0.3MPa, injection speed 8L / min, pressure holding time 2 minutes. Demolding after 12 hours of curing. Repair layer thickness 30mm, actual measured thickness 29.5~31.2mm, flatness 2.8mm / 2m, bonding strength 1.72MPa.

[0282] Example 2-2 (Large size type, used with high wear-resistant putty from Examples 1-3)

[0283] Mold parameters:

[0284] Ditch: 800mm wide, 1000mm high

[0285] Sealing base: Polyurethane foam sealing gasket (25mm thick, 30% compression rate), no inflation required.

[0286] Rigid frame: fiberglass profile, frame spacing 1.0m (due to low rigidity)

[0287] Bottom injection port: Two injection ports connected in parallel, each with an inner diameter of 25mm.

[0288] Top vent valves: 3, 20mm diameter, spaced 0.8m apart.

[0289] Putty formulation: Examples 1-3 (2% steel fiber added, viscosity 7800 mPa·s, yield stress 28 Pa)

[0290] Injection results: Injection pressure 0.4 MPa (due to higher viscosity), injection rate 6 L / min, holding pressure for 3 minutes. Repair layer thickness 40 mm, actual measured 38.5–42.0 mm, abrasion rate 0.58 kg / m². 2 .

[0291] Comparative Example 1 (Mold and mismatched materials)

[0292] Mold: Same as Example 2-1

[0293] Material: Conventional underwater non-dispersible mortar (viscosity 2800 mPa·s, yield stress 9 Pa)

[0294] Results: The grout interface was unstable during the injection process, and the water coming out of the vent valve was always turbid and could not be converted into pure grout. After demolding, a continuous water film was present at the bottom of the repair layer, the bonding strength was only 0.7 MPa, and there were a lot of watermark-like defects on the surface of the repair layer.

[0295] The mold system provided in this embodiment has structural parameters (inflation pressure 0.1–0.15 MPa, frame spacing 1.0–1.5 m, injection port inner diameter ≥25 mm, exhaust valve diameter ≥15 mm) specifically optimized for the rheological properties (yield stress ≥20 Pa, viscosity 5000–8000 mPa·s, slump spread 180–220 mm, maximum aggregate particle size 1.0 mm) of the high-viscosity, high-consistency underwater non-dispersible putty described in Example 1. The two components are matched to achieve bottom-top water injection under non-drainage conditions, completely draining interfacial surface water and obtaining a repair layer with high bonding strength and high density. Replacing any component or material would not achieve the technical effect of this invention. Therefore, this mold system and the putty of Example 1 constitute a unique combination of specific technical features.

[0296] Example 3: Method for improving the wear resistance and corrosion resistance of concrete ditch surfaces after seawater immersion

[0297] This embodiment provides a method for improving the wear and corrosion resistance of concrete trench surfaces immersed in seawater. This method uses the high-viscosity, high-consistency underwater non-dispersible putty described in Example 1, combined with the mold system described in Example 2. Without draining water or altering the water flow path, a bottom-mounted water injection process achieves high-strength bonding and dense filling between the repair layer and the old concrete substrate. The core of this method lies in utilizing the high yield stress (≥20 Pa) and high viscosity (5000~8000 mPa·s) characteristics of the putty from Example 1. Within the sealed cavity formed by the mold system of Example 2, a plunger-like pushing method completely removes accumulated water and loose sediment from the repair area, thereby eliminating the interfacial water film and weak interlayers that are difficult to avoid in traditional underwater repairs. The implementation process and technical principles of this method are described in detail below with specific operational steps.

[0298] Before construction, the ditch to be repaired must first be surveyed, and its width, depth, slope, and water flow velocity must be measured. This method is applicable to seawater ditches with a flow velocity not exceeding 0.5 m / s. When the flow velocity exceeds this value, a temporary baffle plate must be added to the outside of the mold system in Example 2 to reduce the flow velocity around the mold and prevent the sealing base from failing due to water impact. The design thickness of the repair layer is determined according to the degree of wear of the ditch, and is usually 10-50 mm. This thickness range matches the maximum aggregate particle size (1.0 mm) of the putty in Example 1, ensuring that a single layer of filling is sufficient to meet the requirements without causing delamination defects.

[0299] The first step is surface pretreatment. Divers or remotely operated robotic arms use high-pressure water jet equipment to flush the trench walls and bottom, with a water jet pressure of no less than 20 MPa. This pressure is sufficient to remove marine biofilms (such as barnacles and algae), loose corrosion products (such as rust and sulfate crystals), and deposited silt layers attached to the concrete surface, exposing the hard concrete matrix and aggregate, forming a rough interface. The roughness should ideally be such that the exposed aggregate area is ≥50% and the unevenness difference is ≥2 mm, which provides microscopic anchoring points for the mechanical bonding of the subsequent putty. At the same time, a suction pump is used to remove the silt at the bottom, with a suction flow rate of no less than 10 L / min, ensuring that no loose sediment remains in the section to be repaired. After pretreatment, the surface must be inspected by hand by a diver to confirm that there is no oil, no floating mud, and no sharp protrusions (sharp protrusions need to be ground down beforehand to prevent puncturing the sealing base to be installed later). This step differs from conventional underwater repair, which only involves simple rinsing. Instead, it uses a combination of high-pressure water jetting and suction to bring the substrate to a "saturated surface dry" state—the surface is moist but without a flowing water film. This creates optimal conditions for the chemical bonding of the putty in Example 1.

[0300] The second step is mold installation and positioning. The segmented molds described in Example 2 (each segment 2-3m long) are lowered into the water segment by segment, and then assembled longitudinally along the ditch from the lower downstream end to the upper upstream end. During installation, divers first place a rigid support frame across both sides of the ditch, and then use adjusting bolts to ensure the flexible sealing base (inflatable rubber sealing strip or polyurethane foam sealing gasket) at the bottom is tightly against the ditch bottom and sidewalls. The depth to which the adjusting bolts are screwed in determines the gap between the sealing base and the old concrete surface; this gap is the design thickness of the repair layer (e.g., 30mm). Since the putty in Example 1 has a slump expansion of 180-220mm and self-leveling properties, as long as the inner cavity of the mold is flat, the surface of the repair layer can achieve good flatness. Subsequently, the inflatable sealing base is inflated, with the inflation pressure controlled at 0.1-0.15MPa. The pressure was precisely calibrated: below 0.1 MPa, the contact pressure between the sealing strip and the trench wall was insufficient under subsequent injection pressure (0.2–0.4 MPa), potentially causing grout leakage from the bottom; above 0.15 MPa, the rubber strip might over-expand, causing plastic deformation and applying excessive stress to the old concrete. After inflation, divers checked for air bubbles around the mold to ensure good water tightness. Simultaneously, they checked the top venting and drainage channels for unobstructed access, ensuring the vent valve could open properly, and extended the connecting hose above the water surface outside the trench for observation by ground personnel.

[0301] The third step is material grouting, which is the core process of the entire method. The high-viscosity, high-consistency underwater non-dispersible putty, prepared according to the proportions in Example 1, is loaded into the hopper of a piston-type grouting pump. The putty needs to be mixed using a forced mixer. First, add mixing water and liquid polymer flocculant, and stir for 30 seconds. Then add cement, silica fume, quartz sand, and water-reducing agent, and continue stirring for at least 3 minutes to ensure uniformity and no lumps. The mixed putty should be used within 30 minutes to avoid premature cross-linking of the flocculant, which would lead to loss of fluidity. The outlet of the grouting pump is connected to the bottom grouting port (one-way valve) at the lowest point of the mold system in Example 2 via a high-pressure hose. Start the grouting pump and adjust the grouting pressure to 0.2–0.4 MPa, controlling the grouting speed at 5–10 L / min. This pressure range was chosen because the putty in Example 1 has a yield stress ≥20 Pa, exhibiting high structural strength in a static state, but its viscosity decreases under shearing action (such as pumping), showing thixotropy. A pump pressure of 0.2–0.4 MPa is just enough to overcome the flow resistance of the putty in the pipes and molds without being too high and causing the sealing base to fail. The pouring speed of 5–10 L / min is based on the balance between the mold cavity volume (e.g., 2m long × 0.5m wide × 0.03m thick = 0.03m³ = 30L) and the venting efficiency: if the speed is too slow (<5L / min), the putty will stay in the mold for too long, and its thixotropic network may reform and hinder the advancement; if the speed is too fast (>10L / min), the water may not have time to be discharged from the top vent valve, forming local eddies that mix into the putty.

[0302] When the putty enters the mold cavity through the bottom inlet, its density (2200–2300 kg / m³) is slightly higher than that of seawater (approximately 1025 kg / m³), and it possesses high yield stress and high viscosity. Therefore, unlike conventional cement slurry, it does not undergo particle settling or mix with seawater in the water. Instead, the putty exhibits a "plunger-like" overall propulsion pattern, pushing the seawater and air within the mold upwards. The physical mechanism of this process lies in the Bingham fluid properties of the putty in Example 1, which give it a yield stress of over 20 Pa at low shear rates, sufficient to resist convection caused by seawater buoyancy and density differences; simultaneously, its viscosity of 5000–8000 mPa·s provides sufficient viscous resistance to prevent fingering or turbulent mixing at the slurry-water interface. As the putty level rises, the seawater above the mold is forced into the top venting channel and discharged out of the trench through a transparent hose. Ground operators observe the hose outlet: initially, turbid water (containing suspended solids not completely removed during pretreatment) is discharged, gradually becoming clear. Finally, when the putty level reaches the vent valve inlet, the discharged liquid suddenly changes from water to a viscous gray slurry. At this point, immediately close the vent valve and continue maintaining the injection pressure for 2-3 minutes. The purpose of pressure holding is to utilize the putty's micro-expansion characteristics (volume expansion due to the hydration of sulfoaluminate cement to form ettringite) and thixotropic recovery to compensate for the plastic shrinkage before the material hardens, ensuring complete adhesion between the repair layer and the inner wall of the mold, eliminating possible cavitation or honeycombing. After pressure holding is completed, the grouting pump is turned off, and the bottom check valve automatically prevents putty backflow.

[0303] The fourth step is curing and demolding. After pouring, the mold is kept in place, allowing the putty to cure naturally in the underwater environment. Due to the use of sulfoaluminate cement, the initial underwater setting time is controlled at 4-6 hours, and the final strength reaches 60% of the design strength after 12 hours. During this period, chloride and sulfate ions in seawater will not corrode the putty because the hydration products of sulfoaluminate cement are mainly ettringite and alumina, which have strong chloride ion binding capacity. Furthermore, the filling effect of silica fume reduces the porosity to below 5%, hindering the penetration of corrosive media. After 12 hours, the diver slowly opens the vent valve to release pressure, then releases air from the flexible sealing base, causing it to automatically retract and detach from the concrete surface. Subsequently, the longitudinal connecting rods and adjusting bolts of the rigid support frame are removed, and the segmented molds are taken out one by one. If the sealing base adheres to the base surface due to slight grout leakage, it can be separated by cutting along the edges using an underwater cutting tool. After demolding, the repair layer surface is a uniform gray, free of honeycomb, holes, and hollow areas, with a surface flatness of up to 3mm / 2m.

[0304] The fifth step is segmented continuous construction. For ditches longer than a single mold section (2-3m), multiple segments of continuous construction are required. After each segment is repaired, the mold is moved forward (upstream) so that the front end of the next mold section overlaps with the end of the previous repair layer, with an overlap length of no less than 200mm. Before overlapping, the overlap surface must be rinsed with a high-pressure water gun to remove any deposits that may have adhered during curing. At the overlap, a handheld underwater high-frequency vibrator (working frequency 50-100Hz, amplitude 0.5-1.0mm) is used to press against the outer wall of the mold or inserted into the putty layer for auxiliary compaction. During vibration, the principle of "quick insertion and slow withdrawal" should be followed, with each point vibrating for 10-15 seconds, until the putty surface is covered with paste and no large air bubbles escape, ensuring a tight bond between the old and new repair layers and avoiding the formation of cold joints. During vibration, care should be taken to avoid the vibrator touching the sealing base to prevent seal failure. This process is continued segment by segment until the entire ditch is repaired.

[0305] This method can be adapted to different environmental conditions. When the water flow velocity in the ditch is greater than 0.5 m / s but does not exceed 0.8 m / s, a temporary baffle is installed on the outside of the mold. The baffle is made of 3 mm thick 316L stainless steel plate, connected to the rigid frame with M10 bolts. The top of the baffle is 250 mm above the water surface, and the width of the baffle is 80 mm wider than the ditch width. Rubber strips are used to seal both sides. Field tests show that this setup can reduce the flow velocity around the mold to below 0.3 m / s, ensuring effective sealing.

[0306] When the flow velocity in the ditch exceeds 0.8 m / s, this method is not recommended for direct application, as the impact of the water flow may cause seal failure or material dispersion. Under such high-speed flow conditions, it is recommended to take temporary diversion measures (such as setting up a bypass pipe or temporary cofferdam) to reduce the flow velocity in the repair section to below 0.5 m / s before proceeding with this method, or to use a dry repair process instead.

[0307] Tests show that after adding a baffle plate, the mold can withstand a flow velocity of 1.0 m / s without sealing failure. For high-scouring areas (such as bends in drainage ditches or downstream of waterfalls), 1% to 3% of steel fibers (6 to 12 mm in length and 0.2 to 0.3 mm in diameter) can be added to the putty in Example 1, accounting for 1% to 3% of the total weight of the putty. The steel fibers are randomly distributed in three dimensions in the putty, forming a composite reinforcement with the cement stone, and their bridging effect can effectively inhibit abrasion and spalling. According to the proportions of Examples 1-3 (with 2% steel fiber), the abrasion rate of the underwater steel ball method can be reduced from 0.82 kg / m² to 0.58 kg / m², a reduction of about 30%. For emergency repairs of small local defects, the mold system can be simplified by using a handheld small sealing cover in conjunction with a manual grouting gun, miniaturizing the grouting method of this example to achieve rapid single-point repair.

[0308] The technical effectiveness of the method in this embodiment has been verified through field testing. A 30m test section was selected on a drainage ditch of a coastal power plant (seawater salinity 3.2%, flow velocity 0.3m / s, water depth 1.2m), and repairs were carried out according to the steps described above. The repair layer was designed to be 30mm thick, using the putty from Example 1-1 and the mold system from Example 2-1. The total construction time (including mold installation, grouting, curing, demolding, and movement) was approximately 8 hours per section (2.5m), which shortens the construction period by more than 70% compared to the traditional cofferdam drainage dry repair method. Twenty-eight days after the repair was completed, core sampling and testing revealed no visible gaps at the interface between the repair layer and the substrate, with an average bond strength of 1.68 MPa (1.72 MPa at 7 days, slightly increasing after 28 days). The repair layer exhibited high density, with an apparent porosity of only 3.2%. The underwater steel ball abrasion rate was 0.85 kg / m², and the chloride ion permeability coefficient (RCM method) was 0.8 × 10⁻¹² m² / s, only 1 / 5 that of ordinary concrete. In contrast, the control section repaired using conventional underwater non-dispersible mortar spraying had a bond strength of only 0.6 MPa and experienced localized peeling after 6 months of operation. Therefore, this method, through the synergistic effect of the putty from Example 1 and the mold system from Example 2, along with precise control of the bottom-water injection process, achieved high-quality and efficient repair of concrete ditch surfaces under seawater immersion conditions, completely solving the technical challenges of weak interface bonding and poor repair layer durability under non-drainage conditions.

[0309] The method disclosed in this embodiment is characterized by: First, combining the rheological properties (high yield stress, high viscosity) of the high-viscosity putty of Example 1 with the bottom-top water injection process, utilizing the physical properties of the putty itself to actively push up accumulated water and sediment, rather than relying on external drainage or diversion; Second, using the sealed cavity and top venting channel of the mold system of Example 2, providing boundary constraints and venting paths for the plunger-like advancement of the putty, making the replacement process orderly and controllable; Third, by precisely matching parameters such as injection pressure (0.2~0.4MPa), injection speed (5~10L / min), and air pressure (0.1~0.15MPa), the stability of the slurry-water interface is ensured, avoiding the cross-flow mixing common in traditional underwater injection; Fourth, this method does not require changing the original water flow path, does not interrupt the operation of the drainage system, has high construction efficiency, and is widely applicable.

[0310] In summary, this invention provides a method for improving the wear resistance and corrosion resistance of concrete ditch surfaces immersed in seawater. Its core lies in: developing a high-viscosity, high-consistency underwater non-dispersible putty; through a specific combination and precise proportion of sulfoaluminate cement, silica fume, graded quartz sand, polymeric flocculant, and polycarboxylate superplasticizer, the material possesses excellent properties such as yield stress ≥20Pa, viscosity 5000-8000mPa·s, water-to-land strength ratio ≥75%, and bond strength ≥1.5MPa; simultaneously, a mold system matching the rheological properties of this putty is designed, employing an inflatable flexible sealing base and a rigid support frame to form a watertight cavity, and setting a bottom injection interface and a top exhaust and drainage channel; based on this, a pioneering bottom-top water injection construction process is developed, utilizing the high yield stress and high viscosity of the putty to form a plunger-like propulsion, completely expelling accumulated water and air from the ditch without drainage or flow alteration, thoroughly eliminating the interface water film and weak interlayer that are difficult to avoid in traditional underwater repairs. Compared with the closest existing technology, this invention achieves the following significant technical effects: the underwater bonding strength between the repair layer and the substrate is increased by more than 100% (≥1.5MPa), reaching the level of dry construction; the repair layer is dense and honeycomb-free, with an abrasion rate ≤1.0kg / m²; construction efficiency is increased by more than 70%, eliminating the need for cofferdam drainage or alteration of water flow paths, and ensuring uninterrupted drainage system operation; material costs are reduced by more than 50% compared to epoxy-based materials, and the molds are reusable. This invention effectively solves the technical challenge of achieving high-quality wear-resistant and corrosion-resistant repair of seawater-soaked concrete ditches under non-drainage conditions, providing a reliable technical solution for the rapid, economical, and long-term maintenance of marine engineering facilities such as coastal ports, wharves, desalination plants, and coastal power plants, and possesses significant creative and industrial application value.

[0311] 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 high-viscosity, high-consistency, non-dispersible putty for underwater use, characterized in that, The putty has a yield stress ≥20Pa and a viscosity of 5000-8000mPa·s; By weight, its components include: 60-70 parts of sulfoaluminate cement, 5-10 parts of silica fume, 20-30 parts of graded quartz sand with a particle size of 0.1-1.0 mm, 0.8-1.2 parts of polymeric flocculant, 0.5-1.0 parts of polycarboxylate superplasticizer, and a water-cement ratio of 0.25-0.30, wherein the cementing material is the sum of sulfoaluminate cement and silica fume.

2. The high-viscosity, high-consistency, underwater non-dispersible putty according to claim 1, characterized in that, The putty also contains steel fibers, and the amount of steel fibers is 1% to 3% of the total weight of sulfoaluminate cement, silica fume and graded quartz sand.

3. The high-viscosity, high-consistency, underwater non-dispersible putty according to claim 1 or 2, characterized in that, The compressive strength ratio of the putty in amphibious molding specimens is ≥75%, the 7-day bond strength with saturated surface-dry concrete substrate is ≥1.5MPa, and the underwater steel ball abrasion rate is ≤1.0kg / m².

4. A mold system for repairing concrete ditches soaked in seawater, characterized in that, The mold system is used in conjunction with the high-viscosity, high-consistency underwater non-dispersible putty according to any one of claims 1-3, comprising: A flexible sealing base, which is an inflatable rubber sealing strip or a polyurethane foam sealing gasket, is arranged along the junction of the bottom plate and the side wall of the ditch. The inflatable rubber sealing strip forms a watertight barrier by inflation, and the polyurethane foam sealing gasket forms a watertight barrier by compression and deformation. The rigid support frame, assembled from lightweight aluminum alloy or fiberglass profiles, spans both sides of the trench, providing vertical support and template positioning. The frame spacing is 1.0-1.5m. The frame is equipped with adjusting bolts or spiral jacks to adjust the distance between the sealing base and the bottom and sidewalls of the trench, thereby controlling the repair layer thickness to be adjustable within the range of 10-50 mm. The bottom injection port, located at the lowest point of the mold, is a one-way valve injection port used to connect to the delivery pump pipe; The top venting and drainage channel is located at the highest point of the mold and is an openable venting valve with a connecting hose extending out of the trench.

5. The mold system according to claim 4, characterized in that, When the flexible sealing base is an inflatable rubber sealing strip, its inflation pressure is 0.1-0.15 MPa.

6. A method for improving the wear resistance and corrosion resistance of concrete ditch surfaces immersed in seawater, characterized in that, Using the high-viscosity, high-consistency underwater non-dispersible putty according to any one of claims 1-3, and the mold system according to claim 4 or 5, the method includes the following steps: Pretreatment of the base surface: High-pressure water jet is used to flush the trench walls and bottom to remove the biofilm and loose corrosion products, exposing the aggregate to form a rough interface; at the same time, the bottom silt is pumped out to keep the section to be repaired clean. Mold installation and positioning: The segmented molds are lowered into the water and spliced ​​sequentially along the longitudinal direction of the ditch. The sealing base is made to fit tightly against the bottom and side wall of the ditch by adjusting the frame bolts. If an inflatable rubber sealing strip is used, it is inflated to 0.1~0.15 MPa to ensure water tightness. If a polyurethane foam sealing gasket is used, it is compressed and deformed to a compression rate of ≥30% to form a watertight barrier. The top venting channel is also checked to ensure it is unobstructed. Material grouting: A piston-type grouting pump is used to pump the mixed high-viscosity putty into the bottom grouting port. The material forms a plunger-like propulsion in the mold cavity, pushing the accumulated water upwards and draining it out of the trench through the top vent valve. The grouting speed is controlled at 5-10 L / min, and the grouting pressure is 0.2-0.4 MPa. Observe the water discharge from the vent valve. When the discharged liquid changes from accumulated water to viscous slurry, close the vent valve and maintain the pressure for 2-3 minutes. Curing and Demolding: After the material has initially set underwater, slowly release the pressure, remove the mold support, and remove the sealing base; Segmented continuous construction: After each segment is repaired, the mold is moved forward, with an overlap length of not less than 200mm. A handheld vibrator is used to assist in compaction at the overlap.

7. The method according to claim 6, characterized in that, The method is applicable to seawater trenches with a flow velocity ≤0.5m / s, and the repair layer thickness is 10-50mm.

8. The method according to claim 6 or 7, characterized in that, In the pretreatment of the substrate, the pressure of the high-pressure water jet is ≥20MPa, and the suction flow rate for the bottom sludge is ≥10L / min.

9. The method according to claim 6, characterized in that, In the material pouring step, a temporary baffle is added to the outside of the mold to accommodate large flow channels with a flow velocity greater than 0.5 m / s. The temporary baffle is made of stainless steel or aluminum alloy with a thickness of 2-4 mm. It is connected to a rigid support frame by bolts. Its height is 200-300 mm above the water surface, its width is 50-100 mm greater than the width of the channel, and the gap between its two sides and the channel wall is ≤10 mm.

10. The method according to claim 6, characterized in that, When the repair area is a high-scouring area, the high-viscosity, high-consistency underwater non-dispersible putty contains 1% to 3% steel fiber, which accounts for 1% to 3% of the total weight of sulfoaluminate cement, silica fume and graded quartz sand, so that the abrasion rate of the repair layer is reduced by more than 30% compared with the repair layer without steel fiber.

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