Cement underground structure crack repairing grouting material and construction method thereof

Abstract

The invention provides a cement underground structure crack repair grouting material, which is composed of a component A and a component B. The component A comprises the following raw materials by weight: 20-35 parts of dead burned magnesium oxide, 10-20 parts of KHPO, 20-30 parts of fly ash, 10-20 parts of granulated blast furnace slag powder, 1-4 parts of nano SiO, 1-3 parts of delayed hydration microcapsules, and 1-3 parts of water-triggered self-healing microcapsules. The component B is prepared from the following raw materials in parts by weight: 60 to 80 parts of water, 0.5 to 2 parts of polycarboxylate superplasticizer, 0.2 to 0.8 part of retarder and 0.1 to 0.5 part of citric acid. The invention further provides a construction method of the cement underground structure crack repairing grouting material. The cement underground structure crack repairing grouting material provided by the invention has relatively good flowing property and self-healing property, and the setting time is controllable.

Description

Technical Field

[0001] The invention relates to a grouting material, in particular to a grouting material for repairing cracks in a cement underground structure and a construction method thereof. Background Art

[0002] Basement exterior walls, floor slabs, and shield tunnel segments are prone to developing microcracks and water seepage during service. Traditional epoxy, polyurethane, and silicate repair grouting systems suffer from the following issues: insufficient fluidity, preventing low-pressure injection into cracks 0.1-0.5 mm; short and difficult-to-control setting times, leading to pump blockage or terminal setting failure; insufficient early compressive strength, impermeability, and long-term self-healing properties; complex single-powder packaging, hindering rapid on-site operation; and poor durability and poor adhesion to wet substrates. Magnesium phosphate cement has attracted attention for its early strength, excellent adhesion, and shrinkage resistance. However, existing single-component MKPC (metallurgical plasticizer) has limited fluidity, making low-pressure, long-distance grouting and subsequent self-healing difficult. No MPC grouting materials have been publicly reported, either domestically or internationally, that combine high fluidity, controllable setting, micro-expansion, and water-triggered self-healing properties, necessitating a technological breakthrough. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a cement underground structure crack repair grouting material, which has good fluidity and self-healing properties and controllable setting time.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: A grouting material for repairing cracks in cement underground structures is composed of a component A and a component B. The component A comprises the following raw materials in parts by weight: 20-35 parts of dead-burned magnesia, 10-20 parts of KH2PO4, 20-30 parts of fly ash, 10-20 parts of granulated blast furnace slag powder, 1-4 parts of nano-SiO2, 1-3 parts of delayed hydration microcapsules, and 1-3 parts of water-triggered self-healing microcapsules; and the component B comprises the following raw materials in parts by weight: 60-80 parts of water, 0.5-2 parts of a polycarboxylate water reducer, 0.2-0.8 parts of a retarder, and 0.1-0.5 parts of citric acid.

[0005] Furthermore, the mass ratio of component A to component B in the present invention is 1:(0.45-0.55).

[0006] Furthermore, the component B of the present invention further comprises 5-10 parts of propylene glycol or 0.1-1 part of an early strength agent. The propylene glycol is added when the construction temperature is ≤0°C, and the early strength agent is added when the construction temperature is ≥35°C.

[0007] Furthermore, the dead-burned magnesium oxide of the present invention has a D50 of 12-18µm, a D90 ≤ 35µm, and a Blaine specific surface area of ​​600-500m² / g. Such a fineness can dissolve sufficient Mg in 10-30min. 2+To provide early strength and micro expansion, without causing excessive instantaneous heat release or a sharp drop in fluidity due to excessive fineness; the D50 of KH2PO4 is 50-70µm, D90≤120µm, and the Blaine specific surface area is 250-350m² / g. This fineness ensures that KH2PO4 It can be fully dissolved within the 6s shear process of the static mixer, while avoiding excessive surface area and increased water demand caused by too fine particle size; the D50 of fly ash is 6-10µm, D90≤25µm, and the Blaine specific surface area is 300-370m² / g. This particle size is conducive to dense filling without significantly increasing the demand for plasticizer due to extremely fine particles; the D50 of granulated blast furnace slag powder is 8-12µm, D90≤30µm, and the Blaine specific surface area is 380-450m² / g. This particle size window takes into account potential activity and exothermic peak clipping, and can synergistically fill the skeleton with fly ash; nanosilica is fumed nanosilica with an equivalent particle size of 10-20nm and a BET specific surface area of ​​120-200m² / g. It can provide interface densification and early strength without significantly increasing plastic viscosity.

[0008] Furthermore, the preparation steps of the delayed hydration microcapsules of the present invention are: Active magnesium oxide was added to water and dispersed at 25°C and 1200 rpm for 20 min to obtain a magnesium oxide slurry with a mass concentration of 45%. The magnesium oxide slurry was sent to a tower spray dryer and granulated at an inlet air temperature of 160°C and an exhaust air temperature of 75°C to obtain a core material with a D50 of 15µm. The core material was then transferred to a bottom spray fluidized bed and fluidized with air at 50°C. At the same time, a poly (lactic acid-3-hydroxycaproic acid) copolymer melt-extruded at 180°C was sprayed at a speed of 3g / min. -1 The spray coating is carried out at a flow rate of 0.25 m³ / min -1 Under the conditions of air volume and 12% weight gain, a 2µm-thick shell was formed. After fluidized curing at 60°C, the shell was vacuum-dried at 40°C and sieved to a particle size of 80-120µm to produce delayed hydration microcapsules. The delayed hydration microcapsules had a moisture content of ≤0.2wt% and a shell integrity of ≥95%. The water retention effect ensured a delayed hydration time of 30±5 minutes in a slurry at a pH of 3. The particle size was small enough to pass freely through cracks.

[0009] Furthermore, the preparation steps of the water-triggered self-healing microcapsules of the present invention are as follows: MgO, KH2PO4, and K2HPO4 were mixed in a mass ratio of 3:1:0.2 to obtain a mixed powder, and the mixed powder was added to 2 times the weight of water and mixed evenly to obtain a slurry. The slurry was homogenized at 45°C and 1500 rpm to form aqueous phase droplets with an average particle size of 140 µm, which were dispersed in a mineral oil / Span-80 continuous phase with a viscosity of 22 mPa·s. Subsequently, urea-formaldehyde prepolymer was added at a pH of 8.5 and 60°C for condensation. The mixture was cooled to 55°C, the pH was adjusted to 3.8, and the reaction was continued for 2 hours to form a UF shell with a thickness of 1.5 µm. After the system temperature was lowered to 40°C, polymethylene polyphenyl polyisocyanate was sprayed into the shell to form another polyurethane shell with a thickness of 1.5 µm. After centrifugal deoiling, the shell was washed with n-hexane countercurrent, rinsed with 50°C water, and vacuum dried at 45°C. The shell was sieved to a particle size of 120-180 µm to obtain water-triggered self-healing microcapsules. The free formaldehyde content of the water-triggered self-healing microcapsules is ≤0.1 mg / L, and a water pressure of 0.3 MPa triggers 95% gel breakage. After a 7-day water seepage cycle, the permeability of the cracks decreases by three orders of magnitude, demonstrating excellent water-triggered self-healing properties. When secondary water seeps into the pores of the solidified structure, the shell ruptures and Struvite K crystals are generated to fill the cracks, achieving ≥95% watertightness restoration. Furthermore, a particle size of ≥120 µm prevents complete washout in extremely narrow cracks of 0.1 mm, while also rupturing due to the hydraulic pressure differential during water seepage, releasing MgO / KH2PO4 to form Struvite-K crystals and complete self-healing.

[0010] Furthermore, the polycarboxylate water-reducing agent of the present invention contains phosphate groups and carboxylic acid groups, and the dispersion performance retention rate is ≥85% within 48 hours at a pH value of 2-13; and the retention rate is ≥70% within 24 hours at a pH value of 1.

[0011] Furthermore, the retarder of the present invention is borax.

[0012] Furthermore, the early strength agent of the present invention is composed of KH2PO4 and MgCl2 in equal weights.

[0013] Another technical problem to be solved by the present invention is to provide a construction method of the above-mentioned cement underground structure crack repair grouting material.

[0014] In order to solve the above technical problems, the technical solution is: A construction method of a grouting material for repairing cracks in a cement underground structure comprises the following steps: S1. At the construction site, component A and component B are mixed uniformly in a static mixer at a mass ratio of 1:(0.45-0.55) to obtain a cement grouting material for repairing cracks in underground structures; S2. The cement underground structure crack repair grouting material obtained in step S1 is injected into the grouting gun, and the nozzle of the grouting gun is inserted into the crack of the cement underground structure with a width of 0.1-0.5mm and a depth of 10-20mm; S3. Continue grouting with the grouting gun at a push pressure of 0.1-0.2 MPa until grouting returns. Maintain pressure for 5 minutes, then release. Curing is essentially complete within 2 hours. Retest water permeability after 7 days. After 7 days, the crack permeability coefficient should decrease by at least 3 orders of magnitude, and the watertightness recovery rate should be no less than 95%.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) High fluidity and low loss: The microslump of the cement underground structure crack repair grouting material of the present invention is ≥250mm, and the fluidity loss in 30 minutes is ≤5%, which can meet the requirements of long-distance low-pressure grouting; (2) Controllable setting: The slow setting and early strength bidirectional control system of the cement underground structure crack repair grouting material of the present invention enables the setting time to be adjusted as needed within the range of 10-30 minutes; (3) Micro-expansion + self-healing: The delayed hydration microcapsules in the cement underground structure crack repair grouting material of the present invention can compensate for shrinkage, and the water-triggered self-healing microcapsules can restore ≥95% of the water tightness after multiple water seepage cycles; (4) Bonding and strength: The cement underground structure crack repair grouting material of the present invention has a 2h compressive strength of ≥10MPa, a 1d compressive strength of ≥25MPa, and an interface tensile strength of ≥3MPa; (5) Green and low-carbon: The total content of fly ash and slag in the cement underground structure crack repair grouting material of the present invention reaches 40-50%, and CO2 emissions are reduced by about 45% compared with the pure MPC system; (6) Friendly packaging: The two-component cement underground structure crack repair grouting material of the present invention can be prepared and used immediately, avoiding uncontrollable operations such as adding powder and reducing water on site, and improving construction efficiency by more than 30%.

[0016] (7) The present invention can achieve high-flow low-pressure injection, controlled coagulation, micro-expansion compensation and long-term self-healing in micro-cracks with a width of 0.1-0.5 mm, with a 2-hour compressive strength ≥10 MPa, a permeability coefficient reduction of ≥3 orders of magnitude, and a self-healing watertightness recovery of ≥95%. It is suitable for leakage control of basement exterior walls, bottom plates and subway shield segments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present invention, and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 This is a schematic structural diagram of the glue injection gun of the present invention; Figure 2 Schematic diagram of the water-triggering self-healing microcapsule's water contact-rupture-crystallization mechanism of the present invention; Figure 3 This is the 0-30min rheological curve of Example 1 of the present invention; Figure 4 This is a comparison chart of the permeability curves before and after crack grouting and 7-day self-healing using Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to specific embodiments. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention but are not intended to limit the present invention.

[0019] Example 1 Standard formula The cement underground structure crack repair grouting material is composed of component A and component B. Component A includes the following raw materials in parts by weight: 25 parts of dead-burned magnesium oxide, 15 parts of KH2PO4, 25 parts of fly ash, 15 parts of granulated blast furnace slag powder, 2 parts of nano-SiO2, 2 parts of delayed hydration microcapsules, and 2 parts of water-triggered self-healing microcapsules; component B includes the following raw materials in parts by weight: 70 parts of water, 1.2 parts of polycarboxylate water reducer, 0.4 parts of retarder, and 0.3 parts of citric acid. Among them, the D50 of dead-burned magnesium oxide is 12-18µm, D90≤35µm, and the Blaine specific surface area is 600-500m² / g; the D50 of KH2PO4 is 50-70µm, D90≤120µm, and the Blaine specific surface area is 250-350m² / g; the D50 of fly ash is 6-10µm, D90≤25µm, and the Blaine specific surface area is 300-370m² / g; the D50 of granulated blast furnace slag powder is 8-12µm, D90≤30µm, and the Blaine specific surface area is 380-450m² / g; nano-silica is fumed nano-silica with an equivalent particle size of 10-20nm and a BET specific surface area of ​​120-200m² / g; polycarboxylate water reducer contains phosphate and carboxylic acid groups and has a pH value of 2-13. The dispersion performance retention rate is ≥85% within 48 consecutive hours, and the retention rate is ≥70% within 24 hours under pH 1 conditions; the retarder is borax.

[0020] The preparation steps of delayed hydration microcapsules are: Active magnesium oxide was added to water and dispersed at 25°C and 1200 rpm for 20 min to obtain a magnesium oxide slurry with a mass concentration of 45%. The magnesium oxide slurry was sent to a tower spray dryer and granulated at an inlet air temperature of 160°C and an exhaust air temperature of 75°C to obtain a core material with a D50 of 15µm. The core material was then transferred to a bottom spray fluidized bed and fluidized with air at 50°C. At the same time, a poly (lactic acid-3-hydroxycaproic acid) copolymer melt-extruded at 180°C was sprayed at a speed of 3g / min. -1The spray coating is carried out at a flow rate of 0.25 m³ / min -1 A shell with a thickness of 2 μm was formed under the conditions of air volume and weight gain of 12%, and the shell was fluidized and solidified at 60°C and then vacuum dried at 40°C. The microcapsules were sieved to a particle size of 80-120 μm to obtain delayed hydration microcapsules.

[0021] The preparation steps of water-triggered self-healing microcapsules are as follows: MgO, KH2PO4, and K2HPO4 were mixed in a mass ratio of 3:1:0.2 to obtain a mixed powder, and the mixed powder was added to 2 times the weight of water and mixed evenly to obtain a slurry. The slurry was homogenized at 45°C and 1500 rpm to form aqueous phase droplets with an average particle size of 140 µm, which were dispersed in a mineral oil / Span-80 continuous phase with a viscosity of 22 mPa·s. Subsequently, urea-formaldehyde prepolymer was added at a pH of 8.5 and 60°C for condensation. The mixture was cooled to 55°C, the pH was adjusted to 3.8, and the reaction was continued for 2 hours to form a UF shell with a thickness of 1.5 µm. After the system temperature was lowered to 40°C, polymethylene polyphenyl polyisocyanate was sprayed into the shell to form another polyurethane shell with a thickness of 1.5 µm. After centrifugal deoiling, the shell was washed with n-hexane countercurrent, rinsed with 50°C water, and vacuum dried at 45°C. The shell was sieved to a particle size of 120-180 µm to obtain water-triggered self-healing microcapsules.

[0022] The construction method of embodiment 1 comprises the following steps: S1. At the construction site, component A and component B were mixed in a static mixer at a mass ratio of 1:0.48 to obtain a cement grouting material for repairing cracks in underground structures; S2. The cement underground structure crack repair grouting material obtained in step S1 is injected into the grouting gun, and the nozzle of the grouting gun is inserted into the crack with a width of 0.2 mm (a 500 mm × 500 mm × 50 mm C30 concrete slab is cut into a 0.2 mm wide groove crack) to a depth of 15 mm; S3. Use the grouting gun to continuously inject grout at a pushing pressure of 0.1 MPa until grouting returns, maintain the pressure for 5 minutes and then release the pressure. The curing is basically completed in 2 hours, and the water seepage is retested after 7 days.

[0023] In this embodiment, a disposable double-barrel grouting gun is used. Figure 1The double-barrel grouting glue gun is provided with a glue pushing mechanism, a gun body and a glue discharging mechanism from left to right. The glue pushing mechanism includes a push rod rack 1, a handle with a trigger lever 2 and a gear, and a piston connecting rod 3 placed above the push rod rack. The push rod rack 1 is connected to the piston connecting rod 3 and engages with the trigger lever 2. A double-piston assembly 4 is provided in the gun body, and includes two powder barrels 5 and liquid barrels 6 arranged in parallel up and down. The double-piston assembly 4 is connected to the trigger lever 2 through the piston connecting rod 3. The glue discharging mechanism includes a premixing chamber 7, a mixing mechanism 8 and a slurry discharge nozzle 9 arranged in sequence, wherein the mixing mechanism is arranged to be connected to the opening provided in the gun body.

[0024] Specifically, in this embodiment, powder cartridge 5 has a capacity of 300 mL and utilizes a high-capacity, high-rigidity nylon 66 GF30 housing to store dry powder component A. Its volume is proportionally proportional to the 135 mL volume of the liquid cartridge below, perfectly matching the on-site mixing mass ratio of powder to liquid of approximately 1:0.45-0.55, ensuring that the two-phase dosages delivered with each piston stroke are consistently matched.

[0025] Liquid agent cylinder 6 has a capacity of 135-165 mL: it is lined with acid-resistant polypropylene and pre-loaded with component B containing water reducer and retarder. The smaller volume is to balance the density difference between powder and liquid; under the same displacement, powder and liquid are output synchronously according to the designed ratio.

[0026] The double piston assembly 4 is specifically a PTFE sealing head with a stainless steel core shaft, which has low sliding friction and is resistant to chemical corrosion; when pushed, it can squeeze out the contents of the two cylinders at the same time and completely block the exhaust gas.

[0027] The main function of the piston connecting rod 3 is to connect the upper and lower pistons with a coaxial rigid rod to eliminate the stroke difference; CNC processing ensures that the length tolerance is ≤ 0.15 mm and the powder-liquid volume synchronization error is < 1%.

[0028] The push rod rack 1 is mainly a 20CrMnTi tempered rack connected to the piston connecting rod 3 and meshed with the gear of the handle, providing a 10:1 mechanical force increase, so that the operator's grip force is maintained in the range of 70–90 N under a grouting pressure of 0.2 MPa.

[0029] Trigger lever 1 and gear: located inside the handle, converts the short stroke of the trigger into a long stroke thrust; with a rebound spring, the advancement can be stopped by releasing the hand, which is convenient for intermittent grouting and tail pressure control.

[0030] The premixing chamber 7 is located in the φ 10 mm × 30 mm cylindrical area after the confluence of the two cylinder outlets and before the static mixer. The high-speed shearing allows the powder to first infiltrate and break up the thin film liquid, significantly reducing the peak pressure drop of the subsequent static mixer.

[0031] Mixing Mechanism 8: Fixed spiral elements are staggered along the axial direction, creating a fractal flow field of stratification, rotation, and re-stratification. This mechanism achieves a powder-liquid mixing uniformity of ≥ 90% within 6 seconds. Simultaneously, the metal cavity walls dissipate heat release, preventing premature localized gelation.

[0032] Shearable slurry nozzle 9: This PE conical nozzle can be cut on-site to a diameter of 1–3 mm according to the crack width. The small diameter generates a dynamic pressure of 0.1–0.2 MPa and a rapid jet flow, facilitating the injection of slurry into cracks as narrow as 0.1 mm. A check cap at the base of the nozzle prevents backflow and leakage during application.

[0033] Through the coordination of the above components, the device achieves precise quantitative synchronous pushing (connecting rod + rack), rapid initial mixing (premixing chamber) and sufficient homogenization (static mixer), and adapts to 0.1-0.5 mm underground cracks with adjustable dynamic pressure and shearable nozzles, completing low-pressure long-distance grouting within a 20-minute operation window without the risk of pump blockage.

[0034] Figure 2 The diagram shows the water-triggering self-healing microcapsule contact-rupture-crystallization mechanism, which can effectively restore water tightness. After testing, the micro slump of the cement underground structure crack repair grouting material prepared in Example 1 is 262mm, and 250mm is retained in 30 minutes (such as Figure 3 As shown in the figure), the initial setting time is 18 minutes, the final setting time is 27 minutes, and the compressive strength is 11.3 MPa after 2 hours. The repeated water seepage test after 7 days shows that the permeability coefficient has decreased by 3.1 orders of magnitude (as shown in the figure). Figure 4 Micro CT observation showed that Struvite K crystals were filled in the rupture area of ​​the self-healing capsule.

[0035] Example 2 Low temperature construction formula On the basis of Example 1, component B further includes 8 parts of propylene glycol. The initial setting is extended to 22 minutes at 0°C, and the 2-hour compressive strength is 10.1 MPa.

[0036] Example 3 High-temperature rapid plugging formula Based on Example 1, component B also includes 0.8 parts of an early strength agent composed of equal weights of KH2PO4 and MgCl2. At 35°C, the initial setting time is shortened to 8 minutes, the final setting time is 15 minutes, and the compressive strength at 30 minutes is 8 MPa. Example

[0037] The cement underground structure crack repair grouting material is composed of component A and component B. Component A includes the following raw materials in parts by weight: 20 parts of dead-burned magnesium oxide, 10 parts of KH2PO4, 20 parts of fly ash, 10 parts of granulated blast furnace slag powder, 1 part of nano-SiO2, 1 part of delayed hydration microcapsules, and 1 part of water-triggered self-healing microcapsules; component B includes the following raw materials in parts by weight: 60 parts of water, 0.5 parts of polycarboxylate water reducer, 0.2 parts of retarder, and 0.1 parts of citric acid. Among them, the D50 of dead-burned magnesium oxide is 12-18µm, D90≤35µm, and the Blaine specific surface area is 600-500m² / g; the D50 of KH2PO4 is 50-70µm, D90≤120µm, and the Blaine specific surface area is 250-350m² / g; the D50 of fly ash is 6-10µm, D90≤25µm, and the Blaine specific surface area is 300-370m² / g; the D50 of granulated blast furnace slag powder is 8-12µm, D90≤30µm, and the Blaine specific surface area is 380-450m² / g; nano-silica is fumed nano-silica with an equivalent particle size of 10-20nm and a BET specific surface area of ​​120-200m² / g; polycarboxylate water reducer contains phosphate and carboxylic acid groups and has a pH value of 2-13. The dispersion performance retention rate is ≥85% within 48 hours, and the retention rate is ≥70% within 24 hours under the condition of pH 1; the retarder is borax; the preparation method of the delayed hydration microcapsules and the water-triggered self-healing microcapsules is the same as that in Example 1.

[0038] The construction method of embodiment 4 comprises the following steps: S1. At the construction site, component A and component B are mixed in a static mixer at a mass ratio of 1:0.45 to obtain a cement grouting material for repairing cracks in underground structures; S2. The cement underground structure crack repair grouting material obtained in step S1 is injected into the grouting gun, and the nozzle of the grouting gun is inserted into the crack of the cement underground structure with a width of 0.1mm and a depth of 10mm; S3. Use the grouting gun to continuously inject grout at a pushing pressure of 0.1 MPa until grouting returns, maintain the pressure for 5 minutes and then release the pressure. The curing is basically completed in 2 hours, and the water seepage is retested after 7 days. Example

[0039] Based on Example 4, component B further includes 5 parts of propylene glycol. Example

[0040] Based on Example 4, component B further includes 10 parts of propylene glycol. Example

[0041] The cement underground structure crack repair grouting material is composed of component A and component B. Component A includes the following raw materials in parts by weight: 35 parts of dead-burned magnesium oxide, 20 parts of KH2PO4, 30 parts of fly ash, 20 parts of granulated blast furnace slag powder, 4 parts of nano-SiO2, 3 parts of delayed hydration microcapsules, and 3 parts of water-triggered self-healing microcapsules; component B includes the following raw materials in parts by weight: 80 parts of water, 2 parts of polycarboxylate water reducer, 0.8 parts of retarder, and 0.5 parts of citric acid. Among them, the D50 of dead-burned magnesium oxide is 12-18µm, D90≤35µm, and the Blaine specific surface area is 600-500m² / g; the D50 of KH2PO4 is 50-70µm, D90≤120µm, and the Blaine specific surface area is 250-350m² / g; the D50 of fly ash is 6-10µm, D90≤25µm, and the Blaine specific surface area is 300-370m² / g; the D50 of granulated blast furnace slag powder is 8-12µm, D90≤30µm, and the Blaine specific surface area is 380-450m² / g; nano-silica is fumed nano-silica with an equivalent particle size of 10-20nm and a BET specific surface area of ​​120-200m² / g; polycarboxylate water reducer contains phosphate and carboxylic acid groups and has a pH value of 2-13. The dispersion performance retention rate is ≥85% within 48 hours, and the retention rate is ≥70% within 24 hours under the condition of pH 1; the retarder is borax; the preparation method of the delayed hydration microcapsules and the water-triggered self-healing microcapsules is the same as that in Example 1.

[0042] The construction method of Example 7 comprises the following steps: S1. At the construction site, component A and component B are mixed in a static mixer at a mass ratio of 1:0.55 to obtain a cement grouting material for repairing cracks in underground structures; S2. The cement underground structure crack repair grouting material obtained in step S1 is injected into the grouting gun, and the nozzle of the grouting gun is inserted into the crack of the cement underground structure with a width of 0.5mm and a depth of 20mm; S3. Use the grouting gun to continuously inject grout at a pushing pressure of 0.2 MPa until grouting returns, maintain the pressure for 5 minutes and then release the pressure. The curing is basically completed in 2 hours, and the water seepage is retested after 7 days. Example

[0043] Based on Example 7, component B further includes 0.1 part of an early strength agent composed of equal weights of KH2PO4 and MgCl2. Example

[0044] Based on Example 7, component B further includes 1 part of an early strength agent composed of equal weights of KH2PO4 and MgCl2.

[0045] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A grouting material for repairing cracks in cement underground structures, characterized by: The invention is composed of component A and component B. Component A comprises the following raw materials in parts by weight: 20-35 parts of dead-burned magnesium oxide, 10-20 parts of KH2PO4, 20-30 parts of fly ash, 10-20 parts of granulated blast furnace slag powder, 1-4 parts of nano-SiO2, 1-3 parts of delayed hydration microcapsules, and 1-3 parts of water-triggered self-healing microcapsules; and component B comprises the following raw materials in parts by weight: 60-80 parts of water, 0.5-2 parts of polycarboxylate water reducer, 0.2-0.8 parts of retarder, and 0.1-0.5 parts of citric acid.

2. The grouting material for repairing cracks in underground cement structures according to claim 1, characterized in that: The mass ratio of component A to component B is 1:(0.45-0.55).

3. The grouting material for repairing cracks in underground cement structures according to claim 2, characterized in that: The component B further comprises 5-10 parts of propylene glycol or 0.1-1 part of an early strength agent.

4. The grouting material for repairing cracks in underground cement structures according to claim 1, characterized in that: The dead-burned magnesium oxide has a D50 of 12-18µm, a D90 of ≤35µm, and a Bryan specific surface area of ​​600-500m² / g; the KH2PO4 has a D50 of 50-70µm, a D90 of ≤120µm, and a Bryan specific surface area of ​​250-350m² / g; the fly ash has a D50 of 6-10µm, a D90 of ≤25µm, and a Bryan specific surface area of ​​300-370m² / g; the granulated blast furnace slag powder has a D50 of 8-12µm, a D90 of ≤30µm, and a Bryan specific surface area of ​​380-450m² / g; and the nano-silicon dioxide is fumed nano-silicon dioxide, has an equivalent particle size of 10-20nm, and a BET specific surface area of ​​120-200m² / g.

5. The grouting material for repairing cracks in cement underground structures according to claim 1, characterized in that: The preparation steps of the delayed hydration microcapsules are: Active magnesium oxide was added to water and dispersed at 25°C and 1200 rpm for 20 minutes to obtain a magnesium oxide slurry with a mass concentration of 45%. The magnesium oxide slurry was sent to a tower spray dryer and granulated at an inlet air temperature of 160°C and an exhaust air temperature of 75°C to obtain a core material with a D50 of 15µm. The core material was then transferred to a bottom spray fluidized bed and fluidized with air at 50°C. At the same time, a poly (lactic acid-3-hydroxycaproic acid) copolymer melt-extruded at 180°C was sprayed at a speed of 3g / min. -1 The flow rate of spray coating is 0.25m³ / min -1 A shell with a thickness of 2 μm was formed under the conditions of air volume and weight gain of 12%, and the shell was fluidized and solidified at 60°C and then vacuum dried at 40°C. The microcapsules were sieved to a particle size of 80-120 μm to obtain delayed hydration microcapsules.

6. The cement underground structure crack repair grouting material according to claim 1, characterized in that: The preparation steps of the water-triggered self-healing microcapsules are as follows: MgO, KH2PO4, and K2HPO4 were mixed in a mass ratio of 3:1:0.2 to obtain a mixed powder, and the mixed powder was added to 2 times the weight of water and mixed evenly to obtain a slurry. The slurry was homogenized at 45°C and 1500 rpm to form aqueous phase droplets with an average particle size of 140 µm, which were dispersed in a mineral oil / Span-80 continuous phase with a viscosity of 22 mPa·s. Subsequently, urea-formaldehyde prepolymer was added at a pH of 8.5 and 60°C for condensation. The mixture was cooled to 55°C, the pH was adjusted to 3.8, and the reaction was continued for 2 hours to form a UF shell with a thickness of 1.5 µm. After the system temperature was lowered to 40°C, polymethylene polyphenyl polyisocyanate was sprayed into the shell to form another polyurethane shell with a thickness of 1.5 µm. After centrifugal deoiling, the shell was washed with n-hexane countercurrent, rinsed with 50°C water, and vacuum dried at 45°C. The shell was sieved to a particle size of 120-180 µm to obtain water-triggered self-healing microcapsules.

7. The cement underground structure crack repair grouting material according to claim 1, characterized in that: The polycarboxylate water reducer contains a phosphate group and a carboxylic acid group.

8. The cement underground structure crack repair grouting material according to claim 1, characterized in that: The retarder is borax.

9. The grouting material for repairing cracks in underground cement structures according to claim 3, characterized in that: The early strength agent consists of KH2PO4 and MgCl2 in equal weights.

10. A construction method of a cement underground structure crack repair grouting material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. At the construction site, component A and component B are mixed uniformly in a static mixer at a mass ratio of 1:(0.45-0.55) to obtain a cement grouting material for repairing cracks in underground structures; S2. The cement underground structure crack repair grouting material obtained in step S1 is injected into the grouting gun, and the nozzle of the grouting gun is inserted into the crack of the cement underground structure with a width of 0.1-0.5mm and a depth of 10-20mm; S3. Use the grouting gun to continuously inject grout at a pushing pressure of 0.1-0.2MPa until grouting returns. Maintain the pressure for 5 minutes and then release the pressure. The curing is basically completed in 2 hours. Re-test the water seepage after 7 days.

Images