Engineering composite material for repairing and reinforcing inspection well and construction process

Abstract

The invention is applicable to the technical field of municipal pipe network engineering, and provides an engineering composite material for repairing and reinforcing an inspection well and a construction process, the composite material takes sulfur aluminum iron series low-carbon cement as a core gelling component, the core gelling component is matched with fly ash, slag and silica fume to form a low-carbon gelling system, and specific graded quartz sand, PVA fiber and steel fiber are supplemented to form the engineering composite material for repairing and reinforcing the inspection well. By combining the regulation and control properties of a polycarboxylic acid water reducer, a cellulose ether thickening agent and a retarder, ultrahigh toughness and a self-repairing function are realized through a fiber-matrix synergistic toughening mechanism. According to the construction technology, a high-speed self-rotating casting machine with the rotating speed larger than or equal to 2000 rpm is adopted, centrifugal spraying operation is conducted on the old inspection well, and thin layer repairing and rapid maintenance technologies are matched. The three-in-one effect of structure repairing, seismic strengthening and self-repairing functions is achieved, and the problems that a traditional inspection well is low in strength, poor in toughness and long in repairing period are solved.

Description

Technical Field

[0001] This invention relates to the field of municipal pipeline engineering technology, and in particular to an engineering composite material and construction process for repairing and reinforcing inspection wells. Background Technology

[0002] Inspection manholes, as key structures in municipal pipeline systems, undertake important functions such as inspection, dredging, and ventilation, and are widely distributed in urban roads, residential areas, and industrial parks. Currently, most existing inspection manholes in my country are constructed using traditional brick masonry or ordinary concrete. These manholes have revealed the following technical defects during long-term use, seriously affecting the operational safety and durability of municipal pipeline networks: Structural defects: The well wall is prone to cracking (0.5-2mm), spalling, and uneven settlement of the foundation (>50mm), which can lead to structural failure. Interface defect: The well casing interface is not properly sealed, which easily leads to leakage and causes the foundation to be eroded; Seismic defects: Low shear strength (0.5-1.2MPa), with a damage rate exceeding 40% in earthquake-prone areas; Repairing defects: Existing repair methods (such as ordinary mortar, resin materials, and reinforced concrete linings) have problems such as long repair cycles, low bond strength, poor high temperature resistance, inability to inhibit crack propagation, and inability to resist earthquakes.

[0003] With the acceleration of urbanization, the service environment of inspection wells is becoming increasingly complex, and the requirements for their structural strength, durability, seismic resistance, and repair efficiency are constantly increasing. Traditional materials and repair technologies can no longer meet the actual needs of municipal engineering. Developing an engineering composite material and supporting construction technology with high strength, high toughness, impermeability, corrosion resistance, self-healing function, and rapid construction characteristics has become the key to solving the problem of inspection well repair and reinforcement, and has significant engineering value and market prospects. Summary of the Invention

[0004] This invention provides an engineering composite material and construction process for the repair and reinforcement of inspection wells, aiming to achieve a three-in-one repair of "structural repair + seismic reinforcement + self-repair function", so that the inspection wells have high impermeability, strong corrosion resistance, high structural strength, ultra-toughness, excellent seismic performance and rapid construction capability.

[0005] The present invention is achieved as follows: an engineering composite material for repairing and reinforcing inspection wells, comprising, by weight, 60-85 parts of cementitious material, 30-50 parts of aggregate, fiber, and functional additives. The cementitious material is composed of 40-50% sulfur-aluminum-iron low-carbon cement, 15-20% Grade I fly ash, 5-10% S95 grade slag, and 5% silica fume. The chemical characteristics of the sulfur-aluminum-iron low-carbon cement are CaO≥30%, Al2O3≥20%, Fe2O3≥6%, SO3≥8%, and the hydration product is mainly calcium sulfoaluminate hydrate. The aggregate is 0.1-0.3mm quartz sand; The fiber comprises 1.5-3.0% PVA fiber and 0.5-1.5% steel fiber; The functional additives include 0.5-1.0% polycarboxylate superplasticizer, 0.05-0.2% cellulose ether thickener, and 0.1-0.5% wt retarder; The retarder is citric acid or boric acid.

[0006] Preferably, in the hydration products of the sulfur-aluminum-iron-based low-carbon cement, the chemical formula of hydrated calcium sulfoaluminate (ettringite, AFt) is C3A·3CaSO4·32H2O. This component enables the composite material to possess early strength, high strength, micro-expansion and high resistance to sulfate corrosion.

[0007] Preferably, the PVA fiber is the key toughening component, with a diameter of 10-20 μm, a length of 6-12 mm, and a tensile strength ≥1200 MPa; the steel fiber is hook-shaped, with a diameter of 0.5-1.0 mm, a length of 15-25 mm, and a tensile strength ≥1000 MPa. The two work together to achieve the multi-crack characteristic of the composite material.

[0008] Preferably, the polycarboxylate superplasticizer has a solid content of 40-50%, which can control the water-cement ratio of the composite material to ≤0.32; the cellulose ether thickener has a viscosity of 10000-20000 mPa·s, which can adjust the slurry viscosity to 80-120 Pa·s and improve the anti-sag properties during construction.

[0009] This invention also proposes a construction process for repairing and reinforcing inspection wells based on the aforementioned engineering composite materials, comprising the following steps: S1. Inspection well ventilation, dredging, and cleaning: Use an axial flow fan to continuously ventilate the inspection well for ≥30 minutes. After confirming that the concentration of harmful gases in the well is ≤national standard limit, use mechanical dredging equipment to remove silt and debris from the bottom of the well. Then use a high-pressure water gun (pressure 0.6-0.8MPa) to wash the well wall to remove surface dust, oil, and loose layers. After washing, allow it to air dry naturally until the moisture content of the well wall base surface is 5-10%. S2. Inspection of manholes: Use a pipe endoscope to inspect for structural defects in the manhole wall, mark the location, width and distribution of cracks and leaks, and use a leakage detector to test the leakage of the manhole pipe joints and manhole wall to determine the scope of treatment. S3. Crack and Leak Treatment: For cracks with a width < 0.5 mm, apply an interface treatment agent (made of cementitious material and water in a ratio of 1:0.4) with a thickness of 0.2-0.3 mm; for cracks and leaks with a width ≥ 0.5 mm, fill with fine slurry of the composite material of this project, compact with a trowel after filling, and let stand for 2-4 hours until the fine slurry initially sets. S4. On-site mixing of cement-based mortar: According to the above-mentioned engineering composite material ratio, put the cementitious materials and aggregates into a forced mixer and dry mix for 2-3 minutes. Add the fiber and continue to dry mix for 3-4 minutes until the fiber is evenly dispersed. Then add the aqueous solution containing polycarboxylate superplasticizer, cellulose ether thickener and retarder, and stir at 600-800 rpm for 5-8 minutes to make cement-based mortar (i.e. composite material). After testing the mortar viscosity to be 80-120 Pa·s, it is ready for use. S5. Cement-based mortar spraying: A high-speed self-rotating casting machine with a rotation speed of ≥2000rpm is used. The casting machine is equipped with 4 spray nozzles. The spraying pressure is adjusted to 0.3-0.5MPa, and the distance between the spray nozzle and the well wall is 150-250mm to ensure that the spraying direction is perpendicular to the well wall. For repairs without reinforcement, cement-based mortar is directly sprayed to a thickness of 10-15mm. For reinforcement with reinforcement, φ6@200mm steel mesh is tied first (the distance between the steel mesh and the well wall is 5-8mm), and then cement-based mortar is sprayed to a total thickness of 20-25mm. During the spraying process, the casting machine is lifted at a uniform speed of 0.5-1m / min using a winch to ensure uniform spraying thickness. S6. Curing with a curing agent: Within 30 minutes after spraying, apply a water-based silicate curing agent using a high-pressure sprayer. The dosage of the curing agent is 0.2-0.3 kg / m². 2 Ensure even coverage of the well wall surface; during the curing period, control the ambient temperature inside the well to 5-35℃ and humidity ≥60%. When the temperature is below 5℃, cover with an insulation blanket for insulation. After 10 hours of natural curing, test the initial strength of the mortar to be ≥20MPa. Continue curing for 24 hours to ensure that the strength reaches more than 90% of the design value. S7. Construction completed: After the maintenance meets the standards, the flatness, thickness and leakage of the well wall are checked again. After confirming that there are no quality problems, the construction residue in the well is cleaned up and the inspection well can be put into use.

[0010] Preferably, in step S1, a safety barrier needs to be set up at the manhole opening before ventilation. During the ventilation process, the concentration of harmful gases is detected every 15 minutes. If the concentration exceeds the standard, the ventilation time is extended and the number of fans is increased. The thickness and composition of the silt are recorded simultaneously during dredging to assess the impact of the manhole's operating environment on the repair effect.

[0011] Preferably, in step S3, the surface of the crack needs to be polished before applying the interface treatment agent to remove sharp edges. After application, the surface should be left to stand for 10-15 minutes until the interface treatment agent is surface dry before proceeding with subsequent crack filling or spraying operations. After the leak point treatment, a local leakage test needs to be conducted to ensure that there is no leakage before proceeding to the next step.

[0012] Preferably, during the spraying process in step S5, thickness detection points need to be set at different heights (top, middle, and bottom) of the well wall, with 3 detection points set for every 1m of height. After spraying, the thickness is measured with a thickness detector. If the deviation exceeds ±1mm, the spraying speed or lifting speed is adjusted. When there is reinforcement, the steel bars need to be derusted before binding the steel mesh. After derusting, the rust rate on the surface of the steel bars is ≤0.5%.

[0013] Preferably, in step S6, the curing agent needs to be sprayed in two applications, with a 1-hour interval between the first and second applications, to ensure that the penetration depth of the curing agent is ≥1mm. During the curing period, the temperature and humidity inside the well should be checked twice a day and a curing log should be recorded. If it rains or is windy, the wellhead should be closed and rain and wind protection measures should be taken to avoid affecting the curing effect.

[0014] Compared with related technologies, the engineering composite material and construction process for repairing and reinforcing inspection wells provided by this invention have the following beneficial effects: 1. Structural performance is greatly improved Significantly improved compressive strength: The compressive strength of the material of this invention reaches 40-90MPa, which is 100%-300% higher than the 20-30MPa of the traditional technology, and can effectively withstand the stress generated by external loads and foundation settlement. Breakthrough enhancement in tensile and strain resistance: tensile strength reaches 5-12MPa, which is 5-12 times higher than traditional technology; tensile strain reaches 3%-10%, which is 30-100 times that of traditional concrete. When the material fails, it exhibits multi-crack characteristics rather than a single wide crack, which can effectively disperse stress and avoid sudden structural failure. Excellent seismic performance: Through fiber reinforcement and toughness enhancement, the shear strength of the material is greatly improved, and the bearing capacity retention rate of the inspection well under seismic action is >90%, which solves the problem of poor seismic resistance of traditional inspection wells; 2. Significantly improved durability and reliability Doubled impermeability: Impermeability grade ≥ P12, more than double that of traditional technology ≤ P6, effectively preventing the infiltration of groundwater and sewage, and protecting the well structure and surrounding foundation; Extremely strong corrosion resistance: chloride ion diffusion coefficient <1×10 -14 m 2 / s, which is two orders of magnitude lower than traditional technology, has a high corrosion resistance coefficient, can resist the erosion of corrosive media in sewage, and extends the service life of inspection wells; Self-healing function from scratch: 28-day self-healing rate >70%, can automatically repair micro-cracks generated during use, reduce later maintenance costs, and improve the reliability of manhole operation; 3. Construction efficiency is greatly improved. Repair thickness is significantly reduced: unreinforced repair thickness is ≤15mm, and the total thickness of reinforced repair is ≤25mm, which is 60%-70% less than the ≥50mm of traditional repair technology, saving material consumption and construction time. The maintenance cycle is significantly shortened: the initial strength can be formed in 10 hours of natural curing and it can be put into use after 24 hours, which is much shorter than the ≥7-day maintenance cycle of traditional technology, reducing the impact on municipal traffic and pipeline operation. Improved demolding efficiency for new wells: During the preparation of new wells, the material reaches the strength standard in 4 hours, and the demolding time is only 2-4 hours, which is more than 90% shorter than the 24-72 hours of traditional technology, thus improving production efficiency; 4. Outstanding overall benefits Significant cost advantages: Reduced material usage and shorter construction period lower labor, material, and machinery rental costs; at the same time, improved material durability and self-healing function reduce the frequency and cost of later maintenance, resulting in a significant reduction in long-term overall costs; Excellent environmental performance: It adopts a low-carbon cementing system, and the carbon emissions of sulfur-aluminum-iron-based low-carbon cement are reduced by more than 30% compared with ordinary silicate cement. Combined with the utilization of industrial waste such as fly ash and slag, it realizes resource recycling and conforms to the concept of green engineering. Wide range of applications: It is not only suitable for the repair and reinforcement of old manholes, but also for the preparation of new manholes. It can be adapted to manholes of different diameters (DN300-1200) to meet the diverse needs of municipal pipeline projects. Attached Figure Description

[0015] Figure 1 This is a flowchart of the construction process of the present invention; Figure 2 This is a schematic diagram of the microstructure of the engineering composite material of the present invention sprayed on the wall of a manhole; Figure 3 This is a schematic diagram of the microstructure of the composite material of the present invention; Figure 4 This is a structural diagram of the high-speed spin casting machine in this invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] This invention provides an engineering composite material for the repair and reinforcement of inspection wells, comprising, by weight, 60-85 parts of cementitious material, 30-50 parts of aggregate, fiber added by volume percentage, and functional additives added by weight percentage of cementitious material. The cementitious material is composed of 40-50% sulfur-aluminum-iron-based low-carbon cement, 15-20% Grade I fly ash, 5-10% Grade S95 slag, and 5% silica fume. The sulfur-aluminum-iron-based low-carbon cement is the core cementitious component, with chemical characteristics of CaO≥30%, Al2O3≥20%, Fe2O3≥6%, and SO3≥8%, and its hydration product is mainly calcium sulfoaluminate hydrate. This component provides the material with early strength, high strength, micro-expansion, and high resistance to sulfate corrosion, with a 4-hour strength reaching 25MPa. The fly ash acts as an active filler, reducing the heat of hydration and improving later-stage strength. The slag enhances density and corrosion resistance. Silica fume is used to fill micropores, improving strength and density.

[0018] The aggregate is 0.1-0.3mm quartz sand, which is used to optimize the gradation and reduce shrinkage cracks.

[0019] The fiber comprises 1.5-3.0% PVA fiber and 0.5-1.5% steel fiber. The PVA fiber is the key toughening component, providing bridging capabilities for cracks and enabling multi-crack propagation. It has a diameter of 10-20 μm, a length of 6-12 mm, and a tensile strength ≥1200 MPa. The steel fiber is hook-shaped, with a diameter of 0.5-1.0 mm, a length of 15-25 mm, and a tensile strength ≥1000 MPa, used to enhance impact and shear resistance. The synergistic effect of the PVA fiber and steel fiber achieves the multi-crack propagation characteristics of the composite material.

[0020] The functional additives include 0.5-1.0% polycarboxylate superplasticizer, 0.05-0.2% cellulose ether thickener, and 0.1-0.5% wt retarder; steel fibers are used to enhance impact and shear resistance.

[0021] The retarder is citric acid or boric acid, used to adjust the setting time of sulfoaluminate cement, which is beneficial for construction.

[0022] The polycarboxylate superplasticizer has a solid content of 40-50%, which can control the water-cement ratio of the composite material to ≤0.32; the cellulose ether thickener has a viscosity of 10000-20000 mPa·s, which can adjust the slurry viscosity to 80-120 Pa·s and improve the anti-sag properties during construction.

[0023] This invention also proposes a construction process for repairing and reinforcing inspection wells based on the aforementioned engineering composite materials, such as... Figure 1 As shown, it includes the following steps: S1. Inspection well ventilation, dredging, and cleaning: Use an axial flow fan to continuously ventilate the inspection well for ≥30 minutes. After confirming that the concentration of harmful gases in the well is ≤national standard limit, use mechanical dredging equipment to remove silt and debris from the bottom of the well. Then use a high-pressure water gun (pressure 0.6-0.8MPa) to wash the well wall to remove surface dust, oil, and loose layers. After washing, allow it to air dry naturally until the moisture content of the well wall base surface is 5-10%. S2. Inspection of manholes: Use a pipe endoscope to inspect for structural defects in the manhole wall, mark the location, width and distribution of cracks and leaks, and use a leakage detector to test the leakage of the manhole pipe joints and manhole wall to determine the scope of treatment. S3. Crack and Leak Treatment: For cracks with a width < 0.5 mm, apply an interface treatment agent (made of cementitious material and water in a ratio of 1:0.4) with a thickness of 0.2-0.3 mm; for cracks and leaks with a width ≥ 0.5 mm, fill with fine slurry of the composite material of this project, compact with a trowel after filling, and let stand for 2-4 hours until the fine slurry initially sets. S4. On-site mixing of cement-based mortar: According to the above-mentioned engineering composite material ratio, put the cementitious materials and aggregates into a forced mixer and dry mix for 2-3 minutes. Add the fiber and continue to dry mix for 3-4 minutes until the fiber is evenly dispersed. Then add the aqueous solution containing polycarboxylate superplasticizer, cellulose ether thickener and retarder, and stir at 600-800 rpm for 5-8 minutes to make cement-based mortar (i.e. composite material). After testing the mortar viscosity to be 80-120 Pa·s, it is ready for use. S5. Cement-based mortar spraying: A high-speed rotary casting machine with a rotation speed ≥2000rpm is used (in this invention, the casting machine is an RSS-EM manhole centrifugal rotary jet grouting machine, model DN300-1200, such as...) Figure 4 As shown, the casting machine has 4 spray nozzles. The spraying pressure is adjusted to 0.3-0.5MPa, and the distance between the spray nozzle and the well wall is 150-250mm to ensure that the spraying direction is perpendicular to the well wall. For repairs without reinforcement, cement-based mortar is directly sprayed to a thickness of 10-15mm. For reinforcement with reinforcement, φ6@200mm steel mesh is first tied (the distance between the steel mesh and the well wall is 5-8mm), and then cement-based mortar is sprayed to a total thickness of 20-25mm. During the spraying process, the casting machine is lifted at a uniform speed of 0.5-1m / min by a winch to ensure uniform spraying thickness. S6. Curing with a curing agent: Within 30 minutes after spraying, apply a water-based silicate curing agent using a high-pressure sprayer. The dosage of the curing agent is 0.2-0.3 kg / m². 2 Ensure even coverage of the well wall surface; during the curing period, control the ambient temperature inside the well to 5-35℃ and humidity ≥60%. When the temperature is below 5℃, cover with an insulation blanket for insulation. After 10 hours of natural curing, test the initial strength of the mortar to be ≥20MPa. Continue curing for 24 hours to ensure that the strength reaches more than 90% of the design value. S7. Construction completed: After the maintenance meets the standards, the flatness, thickness and leakage of the well wall are checked again. After confirming that there are no quality problems, the construction residue in the well is cleaned up and the inspection well can be put into use.

[0024] Before ventilation in step S1, a safety barrier must be set up at the manhole opening. During ventilation, the concentration of harmful gases must be checked every 15 minutes. If the concentration exceeds the standard, the ventilation time should be extended and the number of fans increased. During dredging, the thickness and composition of the silt should be recorded simultaneously to assess the impact of the manhole's operating environment on the repair effect.

[0025] Before applying the interface treatment agent in step S3, the surface of the crack needs to be polished to remove sharp edges. After application, let it stand for 10-15 minutes until the interface treatment agent is surface dry before proceeding with subsequent crack filling or spraying operations. After the leak point treatment, a local leakage test needs to be conducted to ensure that there is no leakage before proceeding to the next step.

[0026] During the spraying process in step S5, thickness detection points need to be set at different heights (top, middle, and bottom) of the well wall, with 3 detection points set for every 1m of height. After spraying, the thickness is measured with a thickness detector. If the deviation exceeds ±1mm, the spraying speed or lifting speed is adjusted. When there is reinforcement, the steel bars need to be derusted before binding the steel mesh. After derusting, the rust rate on the surface of the steel bars is ≤0.5%.

[0027] In step S6, the curing agent needs to be sprayed in two applications. The second application should be carried out 1 hour after the first application to ensure that the penetration depth of the curing agent is ≥1mm. During the curing period, the temperature and humidity inside the well should be checked twice a day and the curing log should be recorded. If it rains or is windy, the wellhead should be closed and rain and wind protection measures should be taken to avoid affecting the curing effect.

[0028] The high-toughness mortar (i.e., composite material) prepared by the construction process in this invention is sprayed onto the wall of the inspection well in a micro-light state, as shown in the invention. Figure 2 As shown.

[0029] A schematic diagram of the microstructure of the high-toughness mortar in this invention is shown below. Figure 3 As shown.

[0030] The advantages of the engineering composite materials and construction technology for manhole repair and reinforcement provided by this invention are shown in the table below (quantitative comparison).

[0031]

[0032] The present invention will be further described in detail below with reference to specific embodiments.

[0033] Example 1: Engineering composite materials and construction process for unreinforced repair 1. Material proportions (parts by weight) Cementitious materials: 75 parts (37.5 parts sulfur-aluminum-iron low-carbon cement, 15 parts Class I fly ash, 7.5 parts S95 grade slag, 5 parts silica fume) Aggregate: 40 parts (0.1-0.3mm quartz sand) Fibers: 2.0% PVA fiber (volume percentage, diameter 15μm, length 8mm, tensile strength 1300MPa), 1.0% steel fiber (volume percentage, end hook type, diameter 0.8mm, length 20mm, tensile strength 1100MPa). Functional additives: 0.8% polycarboxylate superplasticizer (by weight of cementitious material, solid content 45%), 0.1% cellulose ether thickener (by weight of cementitious material, viscosity 15000 mPa·s), 0.2% citric acid (by weight of cementitious material). 2. Construction Target A brick inspection well on a main road in a city, which has been in use for 5 years, has a diameter of DN800mm and a depth of 3.5m. Previous inspections revealed multiple irregular cracks of 0.2-0.8mm in the well wall, a silt accumulation of about 200mm at the bottom of the well, and slight leakage at the well pipe joint. It needs to be repaired without reinforcement.

[0034] 3. Construction process (1) Ventilation, dredging and cleaning of inspection wells Ventilation: A 1.2m high safety enclosure was set up at the wellhead, and two 2.2kW axial flow fans (outlets facing into the well) were placed there for continuous ventilation for 35 minutes. During this period, a portable hazardous gas detector (detecting hydrogen sulfide, methane, and carbon monoxide) was used to check the concentration every 15 minutes. The first test showed a hydrogen sulfide concentration of 0.01mg / m³. 3 (National standard limit: 0.02 mg / m³) 3 The methane concentration was 0.1% (limit 1%), which meets safety requirements.

[0035] Dredging: A small tracked dredging robot (50kg load capacity) was used to enter the bottom of the well, load silt, gravel, and other debris into sealed bags, and then hoist them to the surface using a winch. Approximately 0.8m of silt was dredged. 3 The silt recorded a sand content of approximately 15% and contained no industrial waste residue.

[0036] Cleaning: Use a high-pressure water gun (working pressure 0.7MPa, nozzle diameter 8mm) to spirally flush the well wall from the bottom to the well opening, focusing on flushing the floating dust and oil around the cracks. After flushing, open the well opening and let it air dry for 8 hours. The moisture content of the well wall base surface was measured to be 7% (meeting the requirement of 5-10%).

[0037] (2) Inspection of manholes Structural defect detection: A high-definition pipe endoscope (1080P resolution, 20mm lens diameter) was inserted into the well and one detection point was taken every 30° along the circumference of the well wall, for a total of 12 detection points. Six cracks were marked (two of which were ≥0.5mm wide and the longest crack was 1.2m long). No broken pieces or exposed reinforcement were found on the well wall.

[0038] Leakage detection: Using a pipe leakage detector (sensitivity 0.01L / min), the well pipe joint (the connection between the DN800mm plastic drainage pipe and the well wall) and the marked cracks were inspected. One joint leakage was found (leakage rate 0.03L / min), and two wide cracks showed signs of water seepage.

[0039] (3) Treatment of cracks and leaks Crack pretreatment: Grind all crack surfaces with an angle grinder (80-mesh grinding wheel) to remove sharp edges and loose layers. The grinding width is 50mm on each side of the crack. After grinding, wipe clean with a dry cloth.

[0040] Narrow crack treatment (width < 0.5 mm, 4 cracks in total): Prepare an interface treatment agent (4 parts of sulfur-aluminum-iron low-carbon cement, 1.2 parts of fly ash, 0.6 parts of slag, 0.4 parts of silica fume, and 2.48 parts of water) according to the cementitious material and water ratio of claim 1. Apply the agent evenly to the crack surface with a brush to a thickness of 0.25 mm. After application, let it stand for 12 minutes until it is surface dry.

[0041] Treatment of wide cracks and leaks (2 cracks ≥ 0.5 mm wide, 1 leak at the interface): Replace the aggregate of the engineering composite material described in claim 1 with 0.08 mm quartz sand to prepare a fine slurry (75 parts cementitious material, 40 parts 0.08 mm quartz sand, unchanged fiber content, unchanged functional additive content, water-cement ratio 0.32); inject the fine slurry into the cracks and leaks using a grouting gun at an injection pressure of 0.2 MPa; after filling, compact the surface with a trowel and let it stand for 3 hours until the fine slurry initially sets (no obvious marks when pressed with a finger); after setting, test again with a leakage detector; the leakage at the leak point is reduced to 0, and there is no water seepage in the wide cracks.

[0042] (4) On-site mixing of cement-based mortar Equipment selection: A mobile forced mixer (mixing capacity 0.5m³) will be used. 3 (700 rpm) Rinse the inside of the mixer with clean water before mixing to ensure there are no residues.

[0043] Feeding sequence: First, add cementitious material (75kg) and aggregate (40kg), and dry mix for 2.5 minutes until uniformly mixed; then add PVA fiber (approximately 1.8kg by volume percentage of 2.0%) and steel fiber (approximately 2.2kg by volume percentage of 1.0%), and continue dry mixing for 3.5 minutes, observing that the fibers do not agglomerate; finally, add an aqueous solution containing polycarboxylate superplasticizer (0.6kg), cellulose ether thickener (0.075kg), and citric acid (0.15kg) (total water volume is approximately 22.5kg based on a water-cement ratio of 0.30), and wet mix for 6 minutes to prepare a uniform cement-based mortar.

[0044] Performance testing: The viscosity of the slurry was measured to be 100 Pa·s using a rotational viscometer (meeting the requirements of 80-120 Pa·s), and the slump was measured to be 50 mm using a slump cone (no segregation). Spraying was started within 25 minutes after mixing was completed.

[0045] (5) Cement-based mortar spraying Equipment debugging: Use a high-speed spin casting machine with a speed of 2200rpm (equipped with 4 spray nozzles, 10mm in diameter), adjust the spraying pressure to 0.4MPa, and keep the distance between the spray nozzle and the well wall 200mm. Use a level to calibrate the spraying direction to be perpendicular to the well wall. Attach one thickness marker (12mm thick) to the bottom, middle (1.75m height), and top (3.2m height) of the well wall.

[0046] Shotcrete operation: Fix the casting machine on the lifting platform at the bottom of the well. After starting the equipment, lift the casting machine at a constant speed of 0.8m / min using a winch and continuously spray along the circumference of the well wall. During the shotcrete process, the thickness is checked once with a laser thickness gauge every 500mm of height to ensure that the deviation is ≤±1mm. The final shotcrete thickness is 12mm (which meets the requirement of 10-15mm for unreinforced repair). The total shotcrete time is about 40 minutes.

[0047] (6) Maintenance by spraying maintenance agent Preparation of curing agent: Use water-based silicate curing agent (30% solid content) and load it into a high-pressure sprayer (working pressure 0.3MPa).

[0048] Spraying operation: Within 25 minutes after the spraying is completed, begin the first application of curing agent, using 0.25 kg / m². 2 (The surface area of ​​the well wall is approximately 8.8m²) 2 The total amount is approximately 2.2 kg, ensuring even coverage without any missed areas. After an interval of 1 hour, apply a second coat with the same amount, and check that the penetration depth of the curing agent is approximately 1.2 mm (meeting the requirement of ≥1 mm).

[0049] Environmental control during curing: A temperature and humidity recorder is suspended inside the well to monitor the ambient temperature at 25℃ and humidity at 72% in real time (meeting the requirements of 5-35℃ and ≥60%). During the curing period, the temperature and humidity are recorded twice a day, at 9:00 AM and 4:00 PM, with no abnormal fluctuations. After 10 hours of curing, the initial strength of the mortar is tested with a rebound hammer and found to be 23MPa (≥20MPa requirement). Curing continues for 24 hours, and the strength rises to 48MPa (reaching 95% of the design value).

[0050] (7) Complete construction Quality inspection: After maintenance meets the standards, the flatness of the well wall is checked with a 2m straightedge, and the deviation is ≤3mm; 30 points are checked with an ultrasonic thickness gauge, and the thickness is within the range of 11-13mm; the entire well is checked again with a leakage detector, and there are no leakage points.

[0051] On-site cleanup: Use a vacuum cleaner to remove construction debris (fiber fragments, mortar dust) from inside the well, remove the wellhead enclosure, and restore the manhole cover; fill out the construction record form, record the construction parameters and test results, and the manhole is officially put into use.

[0052] 4. Performance test results Thirty days after the repair, the inspection well was sampled and tested (three core samples of mortar from the well wall were taken). The results are as follows: Mechanical properties: 28-day compressive strength 52 MPa, tensile strength 7.8 MPa, tensile strain 5.2% (meets the 28-day performance requirements of claim 4); Durability: Permeability grade P15 (≥P12), chloride ion diffusion coefficient 8.5×10 -15 m 2 / s (<1×10) -14 m 2 / s); Self-healing performance: Core sample observation showed that the original 0.3mm wide crack had been completely closed, with a self-healing rate of 78% (>70% requirement).

[0053] A follow-up inspection after 6 months of use showed no new cracks in the well wall and no leakage at the well pipe joints, indicating a stable repair effect.

[0054] Example 2: Engineering composite materials and construction technology for reinforced structures 1. Material proportions (parts by weight) Cementitious materials: 80 parts (40 parts sulfur-aluminum-iron low-carbon cement, 16 parts Grade I fly ash, 8 parts S95 grade slag, 5 parts silica fume) Aggregate: 45 parts (0.1-0.3mm quartz sand) Fibers: 2.5% PVA fiber (volume percentage, diameter 18μm, length 10mm, tensile strength 1400MPa), 1.2% steel fiber (volume percentage, end hook type, diameter 0.9mm, length 22mm, tensile strength 1200MPa). Functional additives: 0.9% polycarboxylate superplasticizer (by weight of cementitious material, solid content 48%), 0.15% cellulose ether thickener (by weight of cementitious material, viscosity 18000 mPa·s), and 0.3% boric acid (by weight of cementitious material). 2. Construction Target An industrial park has a concrete inspection well that has been in use for 8 years. The well has a diameter of DN1000mm and a depth of 4.0m. Due to the subsidence of the surrounding land, three vertical cracks with a length of 1.5-2.0m and a width of 1.0-1.5mm have appeared on the well wall. The concrete strength of the well wall has dropped to C20 in some areas (design strength C30), and it needs to be reinforced and repaired.

[0055] 3. Construction process (1) Ventilation, dredging and cleaning of inspection wells Ventilation: Two 3kW axial flow fans were installed, providing continuous ventilation for 40 minutes; harmful gas detection showed a hydrogen sulfide concentration of 0.008 mg / m³. 3 The methane concentration was 0.08%, which meets safety standards.

[0056] Dredging: Grab bucket dredging equipment (grab bucket capacity 0.1m³) is used. 3 The silt at the bottom of the well was removed, totaling 1.2m. 3 The sludge was found to contain industrial wastewater residue (pH=6.5), and further corrosion protection of the mortar is required.

[0057] Cleaning: The well wall was rinsed with a high-pressure water gun (pressure 0.8MPa), focusing on cleaning the corrosion products in the cracks. After rinsing, it was dried for 10 hours, and the moisture content of the well wall was measured to be 6%.

[0058] (2) Inspection of manholes Structural defect detection: Using a pipe endoscope, in addition to three wide cracks, four honeycomb-like pits (50-100 cm² in area) were found on the well wall. 2 The thickness of the concrete cover was tested and found to be less than 20mm in some areas (designed to be 25mm).

[0059] Leakage detection: The leakage detector found that all three wide cracks had obvious water seepage (maximum leakage rate 0.08L / min), while there was no leakage at the well pipe interface.

[0060] (3) Treatment of cracks and leaks Honeycomb surface treatment: Use a chisel to remove loose concrete to a depth of 5-10mm, and after cleaning, apply an interface treatment agent (mixing ratio as in Example 1) with a thickness of 0.3mm.

[0061] Crack treatment: Grind an area of ​​80mm on both sides of the crack, prepare fine grout (aggregate 0.05-0.1mm quartz sand), fill the crack with low-pressure grouting (pressure 0.25MPa), and let it stand for 4 hours until it sets; after setting, leakage test showed that the leakage was 0.

[0062] (4) On-site mixing of cement-based mortar Mixing control: Forced mixer speed 750rpm, dry mix cementitious material (80kg) and aggregate (45kg) for 3 minutes, add fiber (PVA fiber 2.5% about 2.5kg, steel fiber 1.2% about 3.0kg) and dry mix for 4 minutes; add aqueous solution containing functional additives (water-cement ratio 0.28, total water volume about 22.4kg) and wet mix for 7 minutes.

[0063] Temperature control: Monitor the slurry temperature during mixing. When it reaches 29°C, add ice water (12% of the total water volume, about 2.7 kg). The final slurry temperature stabilizes at 26°C and the viscosity is 110 Pa·s. Spraying is carried out within 28 minutes after mixing is completed.

[0064] (5) Cement-based mortar spraying Reinforcing mesh binding: Use φ6 low carbon steel bars and bind the reinforcing mesh at @200mm intervals. The steel bars are first pickled to remove rust (rust rate reduced to 0.3%). The spacing between the reinforcing mesh and the well wall is 7mm (fixed with spacers).

[0065] Spraying parameters: high-speed spin casting machine speed 2500rpm, spraying pressure 0.45MPa, spray nozzle distance 220mm, winch lifting speed 0.6m / min; 15 thickness detection points are set on the well wall, the total spraying thickness is 22mm (meeting the requirement of 20-25mm for reinforced concrete), and the spraying time is about 65 minutes.

[0066] (6) Maintenance by spraying maintenance agent Curing agent spraying: Apply the curing agent (0.28 kg / m²) within 28 minutes after spraying. 2 A second spraying is applied after a 1-hour interval; the temperature inside the well is controlled at 28℃ and the humidity at 75%. If the temperature is below 5℃, an insulation blanket is prepared (but not used).

[0067] Strength monitoring: 25 MPa after 10 hours of curing, and 62 MPa after 24 hours (95% of the design value).

[0068] (7) Complete construction Inspection and acceptance: The flatness deviation of the well wall is ≤2mm, the thickness deviation is ±0.8mm, and there is no leakage during leakage detection; after cleaning the residue, the inspection well is put into use.

[0069] 4. Performance test results Post-repair test: 28 days later Mechanical properties: compressive strength 78 MPa, tensile strength 10.5 MPa, tensile strain 7.6%; Durability: Permeability grade P18, chloride ion diffusion coefficient 6.2×10 -15 m 2 / s; Seismic performance: Simulated earthquake load test, bearing capacity retention rate of 92% (meets the seismic requirements of the claims).

[0070] An inspection after one year of use showed that the well wall structure was stable, with no new cracks and no rust on the reinforcing bars.

[0071] Example 3: Engineering composite materials and construction technology for new well preparation (adapted to repair process logic) 1. Material proportions (parts by weight) Cementitious materials: 65 parts (32.5 parts of sulfur-aluminum-iron low-carbon cement, 13 parts of Grade I fly ash, 6.5 parts of S95 grade slag, and 5 parts of silica fume) Aggregate: 35 parts (0.1-0.3mm quartz sand) Fibers: 1.8% PVA fiber (volume percentage, diameter 12μm, length 7mm, tensile strength 1250MPa), 0.8% steel fiber (volume percentage, end hook type, diameter 0.7mm, length 18mm, tensile strength 1050MPa). Functional additives: 0.7% polycarboxylate superplasticizer (by weight of cementitious material, solid content 42%), 0.08% cellulose ether thickener (by weight of cementitious material, viscosity 12000 mPa·s), 0.25% citric acid (by weight of cementitious material). 2. Construction Target A newly built residential community requires municipal inspection wells (DN600mm, 3.0m deep) that need to be constructed quickly and have high durability. The material of this invention is used to prepare the new wells.

[0072] 3. Construction process (1) "Ventilation, dredging, and cleaning" are adapted to "Mold preparation and base surface treatment". Mold selection: Use steel mold (inner diameter 600mm, height 3.0m), and apply release agent (polysiloxane type) to the inner wall of the mold; after the mold is installed, use a level to calibrate the verticality (deviation ≤1‰).

[0073] Base surface treatment: The bottom foundation of the mold is leveled with C15 concrete. After leveling, the surface flatness is ≤2mm. It is then moistened with water until the moisture content is 8%.

[0074] (2) "Inspection of manholes" is adapted to "Pre-inspection of molds and materials". Mold inspection: Check the sealing of the mold joints (no leakage) and the uniformity of the mold wall thickness (deviation ≤1mm).

[0075] Material pre-testing: Test the performance indicators of cementitious materials and fibers in advance to ensure that they meet the requirements of claim 1.

[0076] (3) "Crack and Leak Treatment" is adapted to "Mold Defect Repair" Repairing surface scratches on the mold: Use putty to repair minor scratches (depth < 0.5mm) on the inner wall of the mold, and then polish until smooth.

[0077] (4) On-site mixing of cement-based mortar Mixing parameters: Forced mixer speed 650rpm, dry mix cementitious material (65kg) and aggregate (35kg) for 2 minutes, add fiber (PVA fiber 1.8% about 1.5kg, steel fiber 0.8% about 1.8kg) and dry mix for 3 minutes; add aqueous solution containing functional additives (water-cement ratio 0.31, total water volume about 20.2kg), wet mix for 5 minutes, slurry viscosity 90Pa·s.

[0078] (5) Cement-based mortar spraying (adapted to new well pouring logic) Pouring operation: Pour the mortar into the mold and use a vibrator (50mm in diameter) to vibrate in layers (each layer is 500mm high and vibrates for 20 seconds), replacing the centrifugal spraying process of the repair process, to ensure that the mortar is dense.

[0079] (6) Maintenance by spraying maintenance agent Curing treatment: Within 30 minutes after pouring, spray with water-based silicate curing agent (dosage 0.22kg / m). 2 The coating is applied in two coats (1 hour apart); the curing environment is 22℃ and 68% humidity. The strength is 22MPa after 10 hours and 55MPa after 24 hours.

[0080] (7) Complete construction Demolding and testing: After 24 hours of curing, the well wall was demolded and tested for flatness ≤2mm and thickness deviation ±1mm. After 28 days, the compressive strength was tested at 68MPa, the tensile strength at 8.2MPa, and the impermeability grade at P16, which met the design requirements and allowed the well to be put into use.

[0081] 4. Performance test results Inspection of the new well after 3 months of use: Mechanical properties: The compressive strength remained at 66 MPa, with no significant decrease; Durability: Chloride ion diffusion coefficient 7.8 × 10⁻⁶ -15 m 2 / s, no leakage; Construction efficiency: Compared with traditional concrete wells (72 hours demolding time), the demolding time is shortened to 24 hours, and the construction cycle is reduced by 67%.

[0082] In summary, this invention provides a complete solution for the repair and reinforcement of manholes through innovative material formulations and construction techniques. The composite material used in this project is based on low-carbon cement with a sulfur-aluminum-iron matrix. Through a fiber-matrix synergistic toughening mechanism, it achieves a balance between ultra-high toughness, self-healing function, and excellent durability. The centrifugal spraying process, combined with specialized equipment, enables thin-layer repair and rapid construction, significantly improving construction efficiency and repair quality. Compared with existing technologies, this invention has significant advantages in structural performance, durability, construction efficiency, and overall cost. It effectively solves the problems of low strength, poor toughness, and long repair cycles inherent in traditional manholes. It is suitable for the preparation and repair of both new and old manholes and has broad application prospects and promotional value.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. An engineering composite material for repairing and reinforcing inspection wells, characterized in that, By weight, it includes 60-85 parts of cementitious materials, 30-50 parts of aggregates, fibers, and functional additives; The cementitious material is composed of 40-50% sulfur-aluminum-iron low-carbon cement, 15-20% Grade I fly ash, 5-10% S95 grade slag, and 5% silica fume. The chemical characteristics of the sulfur-aluminum-iron low-carbon cement are CaO≥30%, Al2O3≥20%, Fe2O3≥6%, SO3≥8%, and the hydration product is mainly calcium sulfoaluminate hydrate. The aggregate is 0.1-0.3mm quartz sand; The fiber comprises 1.5-3.0% PVA fiber and 0.5-1.5% steel fiber; The functional additives include 0.5-1.0% polycarboxylate superplasticizer, 0.05-0.2% cellulose ether thickener, and 0.1-0.5% wt retarder; The retarder is citric acid or boric acid.

2. The engineering composite material for repairing and reinforcing inspection wells according to claim 1, characterized in that, The chemical formula of calcium sulfoaluminate hydrate in the hydration products of the sulfur-aluminum-iron-based low-carbon cement is C3A·3CaSO4·32H2O.

3. The engineering composite material for repairing and reinforcing inspection wells according to claim 1, characterized in that, The PVA fiber is the key toughening component, with a diameter of 10-20 μm, a length of 6-12 mm, and a tensile strength ≥1200 MPa; the steel fiber is hook-shaped, with a diameter of 0.5-1.0 mm, a length of 15-25 mm, and a tensile strength ≥1000 MPa. The two work together to achieve the multi-crack characteristic of the composite material.

4. The engineering composite material for repairing and reinforcing inspection wells according to claim 1, characterized in that, The polycarboxylate superplasticizer has a solid content of 40-50%, which can control the water-cement ratio of the composite material to ≤0.32; the cellulose ether thickener has a viscosity of 10000-20000 mPa·s, which can adjust the slurry viscosity to 80-120 Pa·s and improve the anti-sag properties during construction.

5. A construction process for repairing and reinforcing inspection wells based on the engineering composite material described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Inspection well ventilation, dredging, and cleaning: Use an axial flow fan to continuously ventilate the inspection well for ≥30 minutes. After testing that the concentration of harmful gases in the well is ≤national standard limit, use mechanical dredging equipment to remove silt and debris from the bottom of the well. Then use a high-pressure water gun to wash the well wall to remove surface dust, oil, and loose layers. After washing, allow it to air dry naturally until the moisture content of the well wall base surface is 5-10%. S2. Inspection of manholes: Use a pipe endoscope to inspect for structural defects in the manhole wall, mark the location, width and distribution of cracks and leaks, and use a leakage detector to test the leakage of the manhole pipe joints and manhole wall to determine the scope of treatment. S3. Crack and Leak Treatment: For cracks with a width < 0.5 mm, apply an interface treatment agent (made of cementitious material and water in a ratio of 1:0.4) with a thickness of 0.2-0.3 mm; for cracks and leaks with a width ≥ 0.5 mm, fill with fine slurry of the composite material of this project, compact with a trowel after filling, and let stand for 2-4 hours until the fine slurry initially sets. S4. On-site mixing of cement-based mortar: According to the above-mentioned engineering composite material ratio, put the cementitious materials and aggregates into a forced mixer and dry mix for 2-3 minutes. Add the fiber and continue to dry mix for 3-4 minutes until the fiber is evenly dispersed. Then add the aqueous solution containing polycarboxylate superplasticizer, cellulose ether thickener and retarder, and stir at 600-800 rpm for 5-8 minutes to make cement-based mortar. After testing the mortar viscosity to be 80-120 Pa·s, it is ready for use. S5. Cement-based mortar spraying: A high-speed self-rotating casting machine with a rotation speed of ≥2000rpm is used. The casting machine is equipped with 4 spray nozzles. The spraying pressure is adjusted to 0.3-0.5MPa, and the distance between the spray nozzle and the well wall is 150-250mm to ensure that the spraying direction is perpendicular to the well wall. For repairs without reinforcement, cement-based mortar is directly sprayed to a thickness of 10-15mm. For reinforcement with reinforcement, φ6@200mm steel mesh is tied first, and then cement-based mortar is sprayed to a total thickness of 20-25mm. During the spraying process, the casting machine is lifted at a uniform speed of 0.5-1m / min using a winch to ensure uniform spraying thickness. S6. Curing with a curing agent: Within 30 minutes after spraying, apply a water-based silicate curing agent using a high-pressure sprayer. The dosage of the curing agent is 0.2-0.3 kg / m². 2 Ensure even coverage of the well wall surface; during the curing period, control the ambient temperature inside the well to 5-35℃ and humidity ≥60%. When the temperature is below 5℃, cover with an insulation blanket for insulation. After 10 hours of natural curing, test the initial strength of the mortar to be ≥20MPa. Continue curing for 24 hours to ensure that the strength reaches more than 90% of the design value. S7. Construction completed: After the maintenance meets the standards, the flatness, thickness and leakage of the well wall are checked again. After confirming that there are no quality problems, the construction residue in the well is cleaned up and the inspection well can be put into use.

6. The construction process for repairing and reinforcing inspection wells according to claim 5, characterized in that, Before ventilation in step S1, a safety barrier must be set up at the manhole opening. During ventilation, the concentration of harmful gases must be checked every 15 minutes. If the concentration exceeds the standard, the ventilation time should be extended and the number of fans increased. During dredging, the thickness and composition of the silt should be recorded simultaneously to assess the impact of the manhole's operating environment on the repair effect.

7. The construction process for repairing and reinforcing inspection wells according to claim 5, characterized in that, Before applying the interface treatment agent in step S3, the surface of the crack needs to be polished to remove sharp edges. After application, let it stand for 10-15 minutes until the interface treatment agent is surface dry before proceeding with subsequent crack filling or spraying operations. After the leak point treatment, a local leakage test needs to be conducted to ensure that there is no leakage before proceeding to the next step.

8. The construction process for repairing and reinforcing inspection wells according to claim 5, characterized in that, During the spraying process in step S5, thickness detection points need to be set at different heights on the well wall, with 3 detection points set for every 1m of height. After spraying, the thickness is measured with a thickness detector. If the deviation exceeds ±1mm, the spraying speed or lifting speed is adjusted. When there is reinforcement, the steel bars need to be derusted before binding the steel mesh. After derusting, the rust rate on the surface of the steel bars is ≤0.5%.

9. The construction process for repairing and reinforcing inspection wells according to claim 5, characterized in that, In step S6, the curing agent needs to be sprayed in two applications. The second application should be carried out 1 hour after the first application to ensure that the penetration depth of the curing agent is ≥1mm. During the curing period, the temperature and humidity inside the well should be checked twice a day and the curing log should be recorded. If it rains or is windy, the wellhead should be closed and rain and wind protection measures should be taken to avoid affecting the curing effect.

Images