Road small box girder crack repairing material and road maintenance application

Abstract

The invention relates to the technical field of road engineering materials, and discloses a road small box girder crack repairing material and road maintenance application. The repairing material is composed of solid-phase powder and liquid-phase slurry; the solid-phase powder comprises dead burned magnesium oxide, quartz sand, micronized carbonate, benzoyl peroxide and an active mineral admixture; the liquid-phase slurry comprises hydroxyethyl methylacrylate, methacrylic acid, water, ammonium dihydrogen phosphate and a silane coupling agent. Chemical heat released by inorganic acid-alkali reaction is utilized to excite organic monomer polymerization, so that rapid curing in a low-temperature environment is realized; and a self-pressurization mechanism is constructed by utilizing in-situ gas production, and slurry is driven to permeate into the deep part of the microcrack and isolate oxygen. The material has the advantages of being high in low-temperature constructability, high in micro-crack permeability, firm in interface bonding, good in impermeability and durability and the like, and is particularly suitable for rapid first-aid repair of concrete bridges and pavement micro-cracks in cold weather.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a road small box girder crack repair material and road maintenance application. BACKGROUND

[0002] The concrete small box girder has been widely used in the construction of expressways and urban bridges due to its good stress performance and economy. However, the small box girder is prone to produce micro cracks with a width of 0.1mm to 3.0mm at the negative bending moment area and flange plate and the like due to the influence of early shrinkage, temperature difference stress and dynamic load fatigue and the like. If these cracks are not repaired in time, water and corrosion medium such as deicing salt will enter along the cracks, leading to corrosion of the steel bars and deterioration of the concrete structure, and seriously affecting the durability and safety of the bridge.

[0003] For such diseases, the existing repair technology mainly uses organic polymer materials such as epoxy resin or polyurethane for grouting repair. However, the curing reaction of such organic materials is highly sensitive to temperature, and when the environmental temperature is lower than 5℃, the reactivity is reduced, resulting in a very long curing time or even no curing; and in the negative temperature environment such as winter in the north, the conventional water-based repair material is more likely to be frozen and fail. In addition, for micro cracks with extremely small width, it is difficult for the traditional gravity penetration method to deliver the high-viscosity repair material to the crack tip, resulting in incomplete repair, and the organic material is easily affected by the air oxygen during the curing process, causing the surface to be sticky and the strength to be insufficient, which is difficult to meet the requirements of road rapid repair and durability. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a road small box girder crack repair material and road maintenance application, which solves the problems of difficulty in curing of organic repair materials in low temperature environment, easy freezing and failure of water-based materials, and difficulty in deep filling of micro cracks by traditional gravity penetration method and easy oxygen inhibition of surface, resulting in poor repair effect.

[0005] To achieve the above purpose, the present application realizes the following technical scheme: A road small box girder crack repair material is composed of a solid powder A component and a liquid slurry B component, and the mass ratio of the solid powder A component to the liquid slurry B component is 3.0:1.0 to 4.5:1.0. The solid powder A component is made of raw materials containing the following weight parts: heavy burned magnesium oxide 40.0 to 60.0 parts, quartz sand 35.0 to 55.0 parts, micro-powdered carbonate 1.0 to 3.5 parts, benzoyl peroxide 1.5 to 3.0 parts, fly ash or silicon powder 2.0 to 5.0 parts; The liquid phase slurry B component is made of raw materials including 60.0-80.0 parts of hydroxyethyl methacrylate, 5.0-15.0 parts of methacrylic acid, 10.0-20.0 parts of water, 25.0-40.0 parts of ammonium dihydrogen phosphate, and 1.0-3.0 parts of silane coupling agent.

[0006] By adopting the technical scheme, the application solves the technical problems of the existing repair material, such as difficult solidification in a low-temperature environment and poor permeability in a micro crack, by using a ternary coupling mechanism of inorganic heat release-chemical gas production-organic polymerization. The specific reaction mechanism and beneficial effects are described as follows: First, a thermodynamic coupling initiation mechanism is established to realize low-temperature spontaneous solidification. After ammonium dihydrogen phosphate and heavy-burned magnesium oxide are mixed, an acid-base neutralization reaction occurs to release a large amount of chemical heat. The internal heat source rapidly increases the core temperature of the slurry to the thermal decomposition temperature of benzoyl peroxide. The free radicals generated by the decomposition further initiate the free radical polymerization reaction of hydroxyethyl methacrylate and methacrylic acid. This process does not require an external heat source, and the inorganic reaction heat is used to initiate the organic reaction in situ, ensuring that the material can still quickly coagulate and harden in a low-temperature environment of-20℃-5℃.

[0007] Second, a gas pressure driven penetration mechanism is constructed to realize self-filling of micro cracks. The acidic monomer and phosphate in the liquid phase contact the micronized carbonate in the solid phase to generate carbon dioxide gas in situ. In the limited crack space, the volume expansion of the gas establishes an internal pressure gradient, which drives the high-viscosity slurry to overcome the capillary resistance and flow to the deep and sharp end of the crack, realizing self-pressurized penetration. At the same time, the continuously overflowing gas forms a gas curtain on the surface of the slurry, effectively excluding the interfacial air and blocking the polymerization inhibition effect of oxygen on the acrylate monomer, solving the problems of surface tackiness and incomplete solidification.

[0008] Third, an organic-inorganic interpenetrating network structure is formed to improve the comprehensive mechanical properties. The cured material is formed by the rigid inorganic framework of magnesium phosphate cement and the flexible organic network of polyacrylate, which are interpenetrated and entangled with each other. The inorganic phase provides high compressive strength and chemical compatibility with the concrete base material, and the organic phase fills the pores and provides toughening effect, significantly reducing the brittleness of the material and improving the crack resistance and interfacial bonding strength of the repair body under dynamic load.

[0009] Preferably, the heavy-burned magnesium oxide is prepared by calcining magnesite at a high temperature of 1500℃-1700℃, the MgO content is ≥90%, and the specific surface area is 200m 2 / kg-400m 2 / kg; the micronized carbonate is sodium bicarbonate or calcium carbonate, and the average particle size D50 thereof is 5-10 μm. By using the above technical solution, high-temperature re-burned magnesium oxide is selected and its specific surface area is controlled, so that the acid-base reaction rate can be accurately controlled, and the reaction is prevented from being too fast to cause insufficient operation time or too slow to cause a low heat release peak and thus unable to initiate polymerization; the particle size of the micronized carbonate is controlled, so that the bubbles are fine and uniform, structural defects caused by large bubbles are avoided, and the gas production rate is ensured to match the viscosity growth rate.

[0010] Preferably, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane; the particle size of the quartz sand ranges from 40 mesh to 70 mesh; and the ammonium dihydrogen phosphate is ground to pass through a 100 mesh sieve before use.

[0011] By using the above technical solution, the silane coupling agent connects the inorganic phase and the organic phase through chemical bonding, eliminates micro defects at the interface between the two phases, significantly reduces the chloride ion permeability coefficient, and improves the durability of the material; and controlling the fineness of the ammonium dihydrogen phosphate is conducive to its dispersion in hydroxyethyl methacrylate and the exertion of its reaction activity.

[0012] Preferably, the preparation method of the liquid-phase slurry B component comprises the following steps: (1) under stirring, the formula amount of hydroxyethyl methacrylate, water and methacrylic acid are sequentially added and uniformly mixed at 20°C±5°C; (2) the stirring speed is increased to 800-1200 rpm, the ammonium dihydrogen phosphate powder is slowly added, and the stirring is continued until a uniform suspension or solution is formed; (3) the formula amount of the silane coupling agent is added, the stirring speed is reduced to 300 rpm, and the stirring is continued for at least 5 minutes before sealing and storage.

[0013] By using the above technical solution, the specific feeding sequence and stirring process ensure the stable dispersion of the ammonium dihydrogen phosphate in the organic monomer system, prevent settling or agglomeration during storage, and ensure the storage stability of the B component.

[0014] Preferably, the preparation method of the solid-phase powder A component comprises the following steps: (1) the formula amount of benzoyl peroxide is premixed with fly ash or silica powder at a ratio of 1:1; (2) the re-burned magnesium oxide, quartz sand, micronized carbonate and the premix obtained in step (1) are put into a mixer and mixed at a speed of 15-25 rpm for 10-15 minutes, and then vacuum packaged after discharging.

[0015] By adopting the technical scheme, the premixing step can prevent trace initiator (BPO) from being unevenly distributed in the powder, avoid local rapid polymerization or non-polymerization phenomenon, and ensure the consistency of the solidification performance.

[0016] In a second aspect, the present application provides a road maintenance application method of a road small box girder crack repair material, which adopts the following technical scheme: A road maintenance application method of a road small box girder crack repair material, comprising the following steps: S1, crack cleaning: high-pressure air is used to blow the crack opening to remove gravel and dust; S2, in-situ mixing of slurry: the measured liquid slurry B component is placed in a container, and the measured solid powder A component is quickly poured into the container under stirring to uniformly mix to obtain a repair slurry; S3, grouting and self-pressurization: the repair slurry is quickly poured or injected along the crack direction, and the gas generated by the internal reaction of the slurry drives the slurry to penetrate into the deep crack; S4, thermal-chemical coupling solidification: the slurry is left to stand, and the chemical heat released by the reaction of the inorganic component excites the polymerization of the organic component to complete the solidification.

[0017] By adopting the technical scheme, the application method discards the dependence on external heating equipment or grouting equipment in the traditional repair technology. Through the in-situ mixing of the slurry and the grouting and self-pressurization steps, the chemical energy of the material itself is converted into heat energy and kinetic energy, realizing efficient construction in a low-temperature, passive environment. The method simplifies the process flow, and is particularly suitable for rapid repair of highways, bridges and other field infrastructure.

[0018] Preferably, in step S2, the mixing time is controlled to be between 30 seconds and 60 seconds; and the construction environment temperature is -20℃ to 5℃. By adopting the technical scheme, controlling the mixing time can prevent the slurry from prematurely heating and thickening in the container, and retain sufficient fluidity for penetration; the definite temperature range defines the applicable working conditions of the method, and embodies its low-temperature resistance characteristics.

[0019] Preferably, in step S3, the width of the crack is 0.1mm to 3.0mm; and the self-pressurization refers to the contact reaction of the acidic component in the liquid slurry B component and the micronized carbonate in the solid powder A component to generate carbon dioxide bubbles, thereby generating a gas pressure driving force. By adopting the technical scheme, for micro cracks with a width of 0.1mm to 3.0mm, traditional gravity grouting is difficult to penetrate, but the internal pressure established by the chemical gas production of the method can effectively press the slurry into the deep crack, realizing full-section repair.

[0020] Preferably, in step S4, the internal core temperature of the slurry spontaneously rises to 60-90 DEG C within 2-4 minutes without applying an external heat source, and the final setting is completed within 15-30 minutes. By adopting the above technical scheme, the rapid spontaneous heating and setting characteristics greatly shorten the curing waiting time, so that the repaired road structure can quickly restore the bearing capacity and open to traffic.

[0021] Preferably, the application method is used for repairing cracks in the negative moment area of a prefabricated small box girder of a highway, sealing shrinkage cracks in a cast-in-place concrete bridge deck, or repairing cracks in a broken cement concrete pavement. By adopting the above technical scheme, the applicability of the technical scheme in a specific engineering field is clarified, and the problem of difficult complete repair of micro cracks in these scenarios is solved.

[0022] The present application provides a road small box girder crack repair material and road maintenance application. Has the following beneficial effects: 1. The present application solves the problem of rapid curing in low temperature environment by constructing the thermodynamic coupling mechanism of inorganic reaction exothermic and organic free radical polymerization. The chemical heat released by the reaction of heavy burned magnesium oxide and phosphate is used as an internal heat source. Under low temperature conditions of-20 DEG C to 5 DEG C, the core temperature of the slurry can be quickly raised to the initiator decomposition temperature, and the polymerization reaction of the methacrylate monomer is excited in situ, so that the material can be quickly hardened without relying on external heating equipment, and the closing time of winter road maintenance is shortened.

[0023] 2. The present application realizes the deep penetration and dense filling of micro cracks by using the self-pressurization driving mechanism constructed by chemical gas production. The reaction of the micromized carbonate and the acidic component in the system generates carbon dioxide gas, which establishes a gas pressure gradient in the confined space, and drives the high viscosity slurry to overcome the capillary resistance and enter the tip of the micro crack of 0.1mm to 3.0mm. At the same time, the continuous overflow of gas forms a gas curtain on the surface, effectively blocking oxygen, overcoming the common oxygen inhibition of acrylate materials, and ensuring the integrity of the repair body.

[0024] 3. The organic-inorganic interpenetrating network structure formed by the present application improves the comprehensive mechanical properties and durability of the repair material. The cured body combines the high early strength of magnesium phosphate cement and the flexibility of polymer, effectively alleviating the brittleness defect of single inorganic material, and enhancing the adaptability to dynamic load. In addition, the chemical bridging effect of silane coupling agent eliminates the two-phase interface defect, so that the repair material and the concrete matrix have excellent low temperature bonding strength and anti-chloride ion permeability, prolonging the service life of the infrastructure. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described in the present application, obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] The main raw materials and reagents used in the following examples and comparative examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0027] Dead-burned magnesium oxide, chemical formula MgO, CAS number 1309-48-4, prepared by calcining at a temperature of more than 1500°C, purity ≥ 90%, specific surface area 200-400 m ² / kg, particle size is a light yellow or white powder that passes through a 200 mesh sieve (≤75 μm).

[0028] Ammonium dihydrogen phosphate, chemical formula NH4H2PO4, CAS number 7722-76-1, industrial grade white crystalline powder, purity ≥ 98%, ground to pass through a 100 mesh sieve before use.

[0029] Hydroxyethyl methacrylate, abbreviated as HEMA, chemical formula C6H 10 O3, CAS number 868-77-9, colorless transparent liquid, purity ≥ 98%, as active monomer and solvent.

[0030] Methacrylic acid, abbreviated as MAA, chemical formula C4H6O2, CAS number 79-41-4, colorless liquid, purity ≥ 99%, as pH regulator and crosslinking monomer.

[0031] Sodium bicarbonate, chemical formula NaHCO3, CAS number 144-55-8, ultra-fine white powder, purity ≥ 99%, average particle size (D50) of 5 μm to 10 μm.

[0032] Calcium carbonate, chemical formula CaCO3, CAS number 471-34-1, ultra-fine white powder, purity ≥ 98%, average particle size (D50) of 5 μm to 10 μm.

[0033] Benzyol peroxide, abbreviated as BPO, chemical formula C 14 H 10 O4, CAS number 94-36-0, white powder, purity ≥ 98%.

[0034] 3-methacryloyloxypropyl trimethoxysilane, trade name KH-570, chemical formula C 10 H 20O5Si, CAS No. 2530-85-0, colorless transparent liquid, purity ≥ 97%.

[0035] Quartz sand, main component silicon dioxide (SiO2), CAS No. 14808-60-7, water washed and dried, particle size distribution 40-70 mesh.

[0036] Silica fume, main component amorphous silicon dioxide, CAS No. 69012-64-2, SiO2content ≥ 92%, average particle size 0.1-0.3 μm.

[0037] The following are preparation examples of solid phase powder (A component) and liquid phase slurry (B component) according to the foregoing technical solutions.

[0038] Preparation examples A1-A3 are for the preparation of solid phase powder (A component). The general preparation process is as follows: first, the formula amount of benzoyl peroxide and silica fume are put into a high-speed mixer for pre-mixing, with a mixing time of 5 minutes to prevent local agglomeration of benzoyl peroxide. Subsequently, dead burned magnesium, quartz sand, sodium bicarbonate (or calcium carbonate) and the aforementioned pre-mixed material are put into a V-type mixer together, mixed at a speed of 20 rpm for 15 minutes, and immediately after discharging, vacuum packaged in a moisture-proof bag.

[0039] Preparation example A1: dead burned magnesium 50.0 kg, quartz sand 45.0 kg, sodium bicarbonate 2.0 kg, benzoyl peroxide 2.0 kg, silica fume 3.0 kg. This formula is a standard type of powder.

[0040] Preparation example A2: dead burned magnesium 45.0 kg, quartz sand 45.0 kg, sodium bicarbonate 3.5 kg, benzoyl peroxide 2.5 kg, silica fume 4.0 kg. The carbonate content in this formula is at a high level, aiming to produce higher gas driving force.

[0041] Preparation example A3: dead burned magnesium 60.0 kg, quartz sand 35.0 kg, calcium carbonate 1.0 kg, benzoyl peroxide 1.5 kg, silica fume 2.5 kg. The magnesium oxide content in this formula is at a high level, the carbonate content is at a low level, and calcium carbonate which has a slower reaction is used.

[0042] Preparation examples B1-B3 are for the preparation of liquid phase slurry (B component). The general preparation process is as follows: in a reaction kettle with a mechanical stirring device, the formula amount of hydroxyethyl methacrylate, water and methacrylic acid are sequentially added, mixed uniformly at a stirring speed of 400 rpm for 5 minutes at 20°C; subsequently, the stirring speed is increased to 1000 rpm, and the ground ammonium dihydrogen phosphate powder is slowly added, continuously stirred for 20 minutes until a uniform and stable milky white suspension or solution is formed; finally, 3-methacryloyloxypropyl trimethoxysilane is added, the stirring speed is reduced to 300 rpm, and stirring is continued for 5 minutes, after which the product is sealed and stored.

[0043] Preparation Example B1: Hydroxyethyl methacrylate 70.0 kg, methacrylic acid 10.0 kg, water 15.0 kg, ammonium dihydrogen phosphate 30.0 kg, 3-methacryloxypropyl trimethoxysilane 2.0 kg. This formulation is a standard type of slurry.

[0044] Preparation Example B2: Hydroxyethyl methacrylate 60.0 kg, methacrylic acid 15.0 kg, water 20.0 kg, ammonium dihydrogen phosphate 40.0 kg, 3-methacryloxypropyl trimethoxysilane 3.0 kg. This formulation has a higher content of acidic components and inorganic reactants, aiming to provide a more intense exothermic reaction and a lower pH environment.

[0045] Preparation Example B3: Hydroxyethyl methacrylate 80.0 kg, methacrylic acid 5.0 kg, water 10.0 kg, ammonium dihydrogen phosphate 25.0 kg, 3-methacryloxypropyl trimethoxysilane 1.0 kg. This formulation has a higher content of active organic monomers, aiming to provide higher flexibility of the cured body. Example 1:

[0046] This example provides a road repair material based on thermal-gas-chemical ternary coupling excitation and a construction method, which is used to repair concrete small box girder cracks with a width of 0.1 mm to 3.0 mm. The simulated environmental temperature of this example is -10°C. The steps include: (1) Preparation of materials: 400 g of solid-phase powder (component A) prepared in Preparation Example A1 is selected, and 100 g of liquid-phase slurry (component B) prepared in Preparation Example B1 is selected. The raw materials and all construction tools are placed in a constant temperature environment box at -10°C for 4 hours to simulate the low temperature working condition on site.

[0047] (2) Mixing: under the -10°C environment, pour the liquid-phase slurry into the stirring container, turn on the handheld stirrer to 600 rpm, quickly add the solid-phase powder, and continue stirring for 45 seconds to prepare the repair slurry with fluidity.

[0048] (3) Grouting and self-pressurization: pour the mixed slurry immediately into the pre-prepared concrete simulated crack test model (crack width 0.2 mm, depth 50 mm). After the slurry enters the crack, the acidic components in the liquid phase react with sodium bicarbonate in the solid phase to generate fine bubbles. A small amount of slurry overflow is observed at the crack opening, indicating that internal gas pressure has driven the slurry to penetrate deeper, and the bubbles overflow carry away the air in the crack.

[0049] (4) Curing: after the slurry fills the crack, it is left to stand without external heating or covering. The slurry temperature rises significantly after about 4 minutes, and the curing is completed in about 20 minutes, forming a surface dense and hard repair body. Example 2:

[0050] This embodiment provides a road repair material and construction method based on thermal-gas-chemical ternary coupling excitation, focusing on the penetration repair of deep microcracks. The simulated environmental temperature of this embodiment is -10°C. The steps include: (1) Preparation of materials: 400 g of solid-phase powder (A component) prepared in Preparation Example A2 is selected, and 100 g of liquid-phase slurry (B component) prepared in Preparation Example B1 is selected. The higher sodium bicarbonate content in Preparation Example A2 aims to provide stronger gas driving force. The raw materials are pre-cooled to -10°C.

[0051] (2) Mixing: In a -10°C environment, the liquid-phase slurry is placed in a container, the stirring speed is set to 800 rpm, the solid-phase powder is quickly added, and stirring is performed for 30 seconds to prepare a low-viscosity slurry.

[0052] (3) Grouting and self-pressurization: The slurry is injected into the crack test mold. Due to the high carbonate content, the slurry produces obvious micro-bubbles immediately upon contact, and the pressure generated by gas expansion pushes the slurry to quickly fill the crack tip.

[0053] (4) Curing: Curing is carried out by relying on the heat released by the magnesium oxide and phosphate reaction inside the system to excite the decomposition of benzoyl peroxide, initiating the polymerization of organic monomers, and completing the final setting within 25 minutes. Example 3:

[0054] This embodiment provides a road repair material and construction method based on thermal-gas-chemical ternary coupling excitation, suitable for extreme low temperature or rapid repair conditions. The simulated environmental temperature of this embodiment is -20°C. The steps include: (1) Preparation of materials: 400 g of solid-phase powder (A component) prepared in Preparation Example A1 is selected, and 100 g of liquid-phase slurry (B component) prepared in Preparation Example B2 is selected. Preparation Example B2 has a higher ammonium dihydrogen phosphate and methacrylic acid content, and the reaction activity and heat release are higher. The raw materials are pre-cooled to -20°C.

[0055] (2) Mixing: In a -20°C environment, the liquid-phase slurry is poured into a stirring container, and the solid-phase powder is added, stirring at 600 rpm for 50 seconds.

[0056] (3) Grouting: The slurry is injected into the crack. Despite the extremely low environmental temperature, the high concentration of acidic components can still react rapidly with carbonates and magnesium oxide.

[0057] (4) Curing: The chemical heat generated by the high-heat-release formula offsets the influence of the extremely low environmental temperature, and the temperature of the slurry rises above 60°C within 5 minutes, ensuring rapid curing within 20 minutes in a -20°C environment. Example 4:

[0058] This example provides a road repair material and construction method based on thermal-gas-chemical ternary coupling excitation, which verifies the influence of different solid-liquid ratios on material performance. The simulated environmental temperature of this example is -5°C. The following steps are included: (1) Preparation: select 300g of solid phase powder (A component) prepared in Preparation Example A1, and select 100g of liquid phase slurry (B component) prepared in Preparation Example B1. At this time, the solid-liquid mass ratio is 3:1, and the proportion of organic components in the system is relatively increased. Pre-cool the raw materials to -5°C.

[0059] (2) Mixing: mix the liquid phase slurry with the solid phase powder and stir for 60 seconds. Due to the increased proportion of liquid phase, the slurry has better flowability and is suitable for very fine cracks.

[0060] (3) Grouting and solidification: inject the slurry into the crack and rely on the internal gas production and oxygen release mechanism and exothermic reaction for solidification. Due to the increased proportion of organic components, the material after solidification shows higher flexibility. Example 5:

[0061] This example provides a road repair material and construction method based on thermal-gas-chemical ternary coupling excitation, which verifies the influence of different solid-liquid ratios on material performance. The simulated environmental temperature of this example is -5°C. The following steps are included: (1) Preparation: select 450g of solid phase powder (A component) prepared in Preparation Example A3, and select 100g of liquid phase slurry (B component) prepared in Preparation Example B3. At this time, the solid-liquid mass ratio is 4.5:1, and calcium carbonate is used as a slow-release gas-producing agent in A3. Pre-cool the raw materials to -5°C.

[0062] (2) Mixing: mix the liquid phase slurry with the solid phase powder and stir for 60 seconds. High solid content makes the slurry more viscous, suitable for filling wider cracks.

[0063] (3) Grouting and solidification: after injection into the crack, the reaction of calcium carbonate with acidic components is relatively gentle, and the gas bubbles are released uniformly and persistently. The reaction heat of magnesium oxide and phosphate initiates polymerization, and solidification is completed within 30 minutes, forming a dense inorganic framework of the repair body with high compressive strength.

[0064] Comparative Example 1: Compared with Example 1, the difference is that in the preparation process of the solid phase powder (A component), instead of adding sodium bicarbonate, an equal amount of quartz sand is used to replace it, i.e. the formula does not contain any micronized carbonate gas-producing component, and the rest of the raw material types, proportions and preparation process are the same as Example 1.

[0065] Comparative Example 2: Compared with Example 1, the difference is that the inorganic exothermic reaction component in the system is removed. Specifically, the heavy-burned magnesium oxide in the solid-phase powder (A component) is replaced with an equal mass of quartz sand; no ammonium dihydrogen phosphate is added in the liquid-phase slurry (B component), and the remaining organic components (HEMA, MAA, BPO, KH-570) remain unchanged. Since no inorganic acid-base reaction occurs, the system has no internal chemical heat source at -10°C, and the remaining mixing and grouting steps are the same as in Example 1.

[0066] Comparative Example 3: Compared with Example 1, the difference is that the organic polymer component in the system is removed. Specifically, in the liquid-phase slurry (B component), an equal volume of water is used to replace the active monomers hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA), and no benzoyl peroxide (BPO) and silane coupling agent is added in the solid-phase powder (A component), only a pure inorganic hydraulic system composed of heavy-burned magnesium oxide, ammonium dihydrogen phosphate, sodium bicarbonate, and filler is retained, and the remaining steps are the same as in Example 1.

[0067] Comparative Example 4: Compared with Example 1, the difference is that a conventional water-based polymer emulsion modification method is used. Specifically, the hydroxyethyl methacrylate (HEMA) in the liquid-phase slurry (B component) is replaced with an equal mass of commercially available water-based acrylic emulsion (solid content 50%), and the original water in the formula is correspondingly deducted to maintain the total water amount consistent, and the system does not contain benzoyl peroxide (BPO), relying on the water evaporation of the emulsion and the hydration of the cement to form a film, and the remaining inorganic components and construction conditions are the same as in Example 1.

[0068] Comparative Example 5: Compared with Example 1, the difference is that no silane coupling agent (KH-570) is added, and the rest is the same as in Example 1.

[0069] Test Example 1: Reaction Kinetics and Curing Process Performance Test in Low Temperature Environment 1. Experimental Description This test aims to verify the workability, reaction exothermicity, and volume stability of the repair materials prepared in the examples and comparative examples under simulated low temperature conditions. The entire experiment is carried out in a temperature-controlled constant temperature test chamber, with the environmental temperature set at -10°C and the relative humidity set at 40%±5%.

[0070] Test Indexes and Methods: (1) Peak temperature of slurry (T max): Determined by K-type thermocouple and multi-channel temperature recorder. The mixed slurry was injected into an adiabatic mold with a diameter of 50 mm and a height of 50 mm. The thermocouple probe was placed at the geometric center of the slurry. The temperature change was recorded at a frequency of 1 second per time until the temperature dropped to ambient temperature. The highest temperature value was read and recorded.

[0071] (2) Setting time: According to GB / T 1346 "Cement Standard Consistency Water Consumption, Setting Time, and Stability Test Method". A standard Vicat apparatus was used for determination. The penetration test was performed every 30 seconds. The initial setting time was defined as the time when the test needle sank to 4 mm ± 1 mm from the bottom plate, and the final setting time was defined as the time when the test needle sank to 0.5 mm.

[0072] (3) Volume change rate: Determined using a graduated transparent polypropylene cylinder. The freshly mixed slurry was injected into the cylinder to the 100 mL graduation line (V0). After compaction, it was placed in a -10°C environment for curing. After 24 hours, the volume of the cured body (V 24 ) was read. The volume change rate calculation formula was: L = (V 24 -V0) / V0 x 100%. A positive value indicates expansion, and a negative value indicates shrinkage.

[0073] (4) State description: Observe and record the macroscopic phenomena during the curing process, such as whether it freezes, whether there is bubble overflow, surface state, etc.

[0074] 2. Experimental results The test data of each example and comparative example is shown in Table 1.

[0075] Table 1: Summary of reaction and curing performance data of repair materials under low temperature (-10°C) environment Group paste peak temperature T max (°C) Initial setting time (min) Final setting time (min) 24h volume change rate (%) Curing state description Example 1 72.4 14.5 19.2 +1.25 Cured completely, surface hard and compact Example 2 68.9 13.8 18.5 +3.42 Cured completely, obvious bubble overflow Example 3 81.3 9.2 13.4 +1.56 Reaction is violent, harden rapidly Example 4 58.7 18.6 26.8 +0.95 Cured slowly, surface slightly elastic Example 5 76.5 11.4 16.1 +0.42 Harden very fast, volume basically constant Comparative Example 1 73.1 15.2 20.4 -2.18 Cured, surface slightly concave shrinkage Comparative Example 2 -9.8 >1440 No setting -- Slurry is in flow state, no curing occurs Comparative Example 3 75.8 8.5 11.2 -0.35 Cured very fast, micro-cracks appear on surface Comparative Example 4 - - - - Internal freezing of slurry, failure Comparative Example 5 71.9 14.8 19.6 +1.18 Cured normally, appearance similar to Example 1 According to the test data in Table 1 and the reaction mechanism of the technical solution of the present application, the following conclusions are drawn: (1) The decisive role of internal heat source in low temperature curing: The peak temperature of the slurry center of Examples 1-5 is between 58°C and 81°C, indicating that the acid-base reaction of phosphate and heavy-burned magnesium oxide can still effectively start and release a large amount of chemical heat at -10°C low temperature. In contrast, Comparative Example 2 removes the inorganic exothermic component, and the slurry temperature remains near the ambient temperature, resulting in the inability of benzoyl peroxide to decompose and the inability of organic monomers to polymerize. The slurry remains in a fluid state. This confirms that the heat provided by inorganic reaction is a prerequisite for organic polymerization reaction to occur, and there is a clear thermodynamic coupling relationship between the two.

[0076] (2) Volume compensation effect of gas generating component: The volume change rates of Examples 1-5 are all positive values, showing the characteristics of micro-expansion. This is because the carbonated gas generated by the reaction of the micronized carbonate and the acidic component forms a micro-pore structure inside the slurry, effectively offsetting the volume shrinkage during the polymerization of organic monomers and the hydration of inorganic components. Comparative Example 1, which does not add a gas-producing component, shows a volume shrinkage of -2.18%, which can easily lead to debonding of the repair material at the crack interface. Example 2, with the highest carbonate content, has the largest volume expansion rate, verifying the kinetic effect of gas generation.

[0077] (3) Low-temperature adaptability of the system: Comparative Example 4 uses a traditional water-based emulsion, which undergoes ice-induced demulsification at -10°C, making it impossible to be shaped. However, the examples of the present application use organic monomers such as hydroxyethyl methacrylate as solvents, combined with inorganic exothermic reactions, completely overcoming the freezing problem of water media below the freezing point, and achieving rapid final setting in a low-temperature environment.

[0078] (4) Component ratio control of process parameters: As can be seen from Comparative Example 3 and Example 4, increasing the concentration of inorganic components and acids can significantly increase the peak temperature and shorten the setting time, which is suitable for rapid repair; while increasing the proportion of organic components reduces the reaction intensity and extends the operable window, which is suitable for fine repair with higher exothermic control requirements.

[0079] Test Example 2: Physical and mechanical properties, interfacial bonding properties, and durability testing 1. Experimental description This test evaluates the mechanical strength, penetration and filling ability for micro-cracks, interfacial bonding stability, and resistance to medium penetration of each example and comparative example after curing. The preparation and curing process of all test pieces are carried out in a -10°C constant temperature chamber, and the test pieces are moved to a normal temperature environment for 2 hours before testing to eliminate the influence of temperature stress.

[0080] Test items and methods: (1) Self-pressurized penetration depth: Two pieces of tempered glass plates with smooth surfaces are clamped to make a simulated crack model, with a fixed crack width of 0.2mm and a crack depth of 100mm, and the two sides and the bottom are sealed. The slurry is naturally poured from the top opening without external pressure. After curing, the actual vertical filling depth of the slurry in the crack model is measured by a vernier caliper. This index represents the self-driven penetration ability of the material relying on chemical gas generation.

[0081] (2) Surface hardness (Shore D): used to evaluate the influence of oxygen inhibition on the surface of the material. The test block after curing for 24 hours is directly measured for the hardness of the top surface exposed to air. Five different points are selected for measurement, and the average value is taken. The lower the value, the more serious the influence of oxygen inhibition on the surface (tacky or uncured).

[0082] (3) Compressive strength: The grout was poured into a triple steel mold of 40mm×40mm×160mm and cured at -10℃. The compressive strength was measured after 1 hour (early strength) and 24 hours (later strength).

[0083] (4) Low-temperature flexural bond strength: The "new and old concrete bonding method" was adopted. A half-size C50 concrete substrate (with roughened surface treatment) was precast and frozen at -10℃ for 24 hours. Then, the repair grout was poured into the remaining space to form a complete prism specimen. After curing at -10℃ for 24 hours, a three-point flexural test was performed, and the fracture load was recorded. If the fracture occurred at the bond interface, the bond strength was calculated; if the fracture occurred in the substrate, it was recorded as substrate failure.

[0084] (5) Chloride ion permeability coefficient (D R CM): The resistance of specimens to chloride ion penetration under an electric field was tested using the RCM (unsteady-state chloride ion migration method) after 28 days of curing. Lower values ​​indicate better density.

[0085] 2. Experimental Results The performance test data for each group are detailed in Table 2.

[0086] Table 2 Summary of test data on the physical, mechanical and durability properties of repair materials Group Self-pressurized penetration depth (mm) Surface hardness (Shore D) Compressive strength-1h (MPa) Compressive strength-24h (MPa) Low temperature bending adhesive strength (MPa) Chloride permeability coefficient (10 −12 m 2 / s)]]> Example 1 94.5 78.4 28.6 62.3 6.8 (matrix failure) 2.4 Example 2 99.8 (full filling) 76.2 25.1 58.9 7.1 (matrix failure) 2.8 Example 3 92.1 80.5 33.4 65.7 6.4 2.1 Example 4 95.3 72.8 18.9 45.2 8.2 (matrix failure) 3.5 Example 5 88.6 82.1 35.2 71.4 5.3 1.8 Comparative Example 1 24.3 45.6 29.1 63.5 4.8 (interface failure) 5.9 Comparative Example 2 -- -- -- -- -- -- Comparative Example 3 86.2 85.4 38.6 75.2 1.9 (interface peeling) 9.4 Comparative Example 4 -- -- -- -- -- -- Comparative Example 5 93.8 77.9 27.8 60.1 4.1 (interface failure) 6.2 (1) The contribution of chemical aerodynamic mechanism to deep penetration and antioxidant inhibition: The penetration depths of Examples 1-5 ranged from 88.6 mm to 99.8 mm, with Example 2, which had a higher carbonate content, achieving full-depth filling. In contrast, Comparative Example 1, which contained no gas-generating components, penetrated only 24.3 mm by gravity. This confirms that the carbon dioxide gas generated in situ within the system established an effective gas pressure-driven mechanism, propelling the high-viscosity slurry to overcome capillary resistance and flow towards the crack tip. Furthermore, the surface hardness of Comparative Example 1 was only 45.6 HD, and a viscous liquid film was observed on the surface, while the surface hardness of the Example groups all exceeded 70 HD. This indicates that the gas generated by the reaction formed a continuous gas curtain on the slurry surface, effectively excluding air and blocking the inhibitory effect of oxygen on the free radical polymerization of acrylates.

[0087] (2) Enhancement of mechanical properties by inorganic-organic interpenetrating networks: Comparative Example 1 and Comparative Example 3 (pure inorganic system) can be seen that although Comparative Example 3 has a higher compressive strength, its low-temperature bending adhesive strength is extremely low, and the failure mode is interfacial brittle peeling. After introducing the organic network in Example 1, although the compressive strength is slightly reduced, the adhesive strength is increased to 6.8 MPa, and the failure occurs in the concrete matrix. This shows that the organic polymer chain forms an effective interpenetrating anchoring structure in the gap and interfacial pore of the inorganic skeleton, which significantly improves the toughness and interfacial compatibility of the material.

[0088] (3) Improvement of durability by interfacial modifier: The chloride ion permeability coefficient of Example 1 is significantly lower than that of Comparative Example 5 without adding silane coupling agent. Without adding the coupling agent, there are micro-interface defects between the inorganic phase and the organic phase, which become the channel for ion transmission. The silane coupling agent connects the two-phase interface through chemical bonding, closes the micro-pores, and thus improves the impermeability and durability of the material.

[0089] (4) Performance regulation characteristics of each example: Example 4 obtains the highest adhesive strength by increasing the content of organic components, but sacrifices part of the compressive strength, which is suitable for dynamic load cracks with high requirements for deformation resistance; Example 5 obtains the highest compressive strength by increasing the inorganic components, which is suitable for static pressure cracks. The adjustability of such performance verifies the flexibility of the formulation system of the present application.

[0090] The self-pressurizing repair material based on thermal-gas-chemical ternary coupling excitation and its construction method provided by the present application have excellent industrial practicability, and are particularly suitable for deep micro-crack treatment and structure reinforcement of concrete infrastructure under cold climate conditions. The specific application scenarios include but are not limited to: early micro-crack repair of negative moment area of precast small box girder of expressway, shrinkage crack sealing of cast-in-place concrete bridge deck, emergency repair of broken slab cracks of cement concrete pavement and airport runway, and anti-seepage treatment of surface micro-cracks of water conservancy dam.

[0091] In actual road maintenance engineering, the repair material solves the industry common problem that traditional organic repair materials cannot be cured at low temperature (-20℃ to 5℃) due to low reactivity, and that water-based repair materials fail below freezing point. Using its unique internal chemical heat source excitation mechanism, construction personnel do not need to carry heating equipment such as generators and hot air guns, and do not need to perform forced drying treatment on the cracks, so that rapid construction can be realized in freezing and humid harsh working conditions.

[0092] Meanwhile, for the micro cracks with width of 0.1-3.0 mm, the material overcomes the defect that traditional gravity permeation method cannot reach the crack tip by using the self-pressurized pneumatic mechanism constructed by in-situ gas production, and realizes the automatic filling and repair of deep disease. The gas curtain produced effectively prevents the surface tackiness problem caused by oxygen inhibition. The repaired structure has high early strength, excellent low-temperature bonding performance with the matrix, and good resistance to chloride ion penetration. The traffic can be opened within 1 hour after the construction is completed, greatly shortening the road closure time and significantly reducing the maintenance cost and traffic pressure. In addition, the material system does not contain volatile organic solvents, which meets the green and environmental protection development trend of road maintenance materials.

Claims

1. A material for repairing cracks in road box girders, characterized in that, It is composed of solid powder component A and liquid slurry component B, wherein the mass ratio of solid powder component A to liquid slurry component B is 3.0:1.0 to 4.5:1.0; The solid powder component A is made from the following raw materials in parts by weight: 40.0-60.0 parts of calcined magnesium oxide, 35.0-55.0 parts of quartz sand, 1.0-3.5 parts of micronized carbonate, 1.5-3.0 parts of benzoyl peroxide, and 2.0-5.0 parts of fly ash or silica powder. The liquid slurry component B is made from the following raw materials in parts by weight: 60.0-80.0 parts of hydroxyethyl methacrylate, 5.0-15.0 parts of methacrylic acid, 10.0-20.0 parts of water, 25.0-40.0 parts of ammonium dihydrogen phosphate, and 1.0-3.0 parts of silane coupling agent.

2. The road small box girder crack repair material according to claim 1, characterized in that, The recalcined magnesite is obtained by calcining magnesite at a high temperature of 1500℃~1700℃, with an MgO content ≥90% and a specific surface area of ​​200m². 2 / kg~400m 2 / kg; The micronized carbonate is sodium bicarbonate or calcium carbonate, with an average particle size D50 of 5 μm to 10 μm.

3. The road small box girder crack repair material according to claim 1, characterized in that, The silane coupling agent is γ-methacryloxypropyltrimethoxysilane; The particle size range of the quartz sand is 40 mesh to 70 mesh; the ammonium dihydrogen phosphate is ground until it passes through a 100 mesh sieve before use.

4. The road small box girder crack repair material according to claim 1, characterized in that, The preparation method of component B of the liquid slurry includes the following steps: 1) While stirring, add the formulated amounts of hydroxyethyl methacrylate, water, and methacrylic acid in sequence, and mix thoroughly at 20℃±5℃; 2) Increase the stirring speed to 800 rpm to 1200 rpm, slowly add ammonium dihydrogen phosphate powder, and continue stirring until a uniform suspension or solution is formed; 3) Add the amount of silane coupling agent specified in the formula, reduce the stirring speed to 300 rpm, continue stirring for at least 5 minutes, and then seal and store.

5. The road small box girder crack repair material according to claim 1, characterized in that, The preparation method of the solid powder component A includes the following steps: 1) Premix the benzoyl peroxide in the formula with fly ash or silica powder in a 1:1 ratio; 2) Add the calcined magnesium oxide, quartz sand, micronized carbonate and the premix obtained in step S1 into a mixer and mix for 10 to 15 minutes at a speed of 15 rpm to 25 rpm. After discharge, vacuum seal the mixture.

6. A method for road maintenance application of a road small box girder crack repair material, applied to the road small box girder crack repair material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Crack cleaning: Use high-pressure air to blow away the crack openings and remove debris and dust; S2. In-situ mixing of slurry: Place the metered liquid phase slurry component B in a container, and quickly pour in the metered solid phase powder component A while stirring. Mix evenly to obtain the repair slurry. S3. Grouting and self-pressurization: The repair grout is quickly poured or injected along the crack direction, and the gas generated by the internal reaction of the grout drives the grout to penetrate into the depth of the crack. S4. Thermal-chemical coupling curing: The slurry is left to stand, and the organic components are polymerized by the chemical heat released by the reaction of the inorganic components, thus completing the curing process.

7. The road maintenance application method of the road small box girder crack repair material according to claim 6, characterized in that, In step S2, the mixing time is controlled between 30 and 60 seconds, and the ambient temperature during construction is between -20℃ and 5℃.

8. The road maintenance application method of the road small box girder crack repair material according to claim 6, characterized in that, In step S3, the width of the crack is 0.1 mm to 3.0 mm; Self-pressurization refers to the reaction between the acidic component in the liquid slurry (component B) and the micronized carbonate in the solid powder (component A) to generate carbon dioxide bubbles, thereby producing a pressure driving force.

9. The road maintenance application method of the road small box girder crack repair material according to claim 6, characterized in that, In step S4, without the application of an external heat source, the core temperature inside the slurry spontaneously rises to 60°C to 90°C within 2 to 4 minutes, and final setting is completed within 15 to 30 minutes.

10. The road maintenance application method of the road small box girder crack repair material according to claim 6, characterized in that, The application method is used for repairing cracks in the negative bending moment zone of precast small box girders on highways, sealing shrinkage cracks in cast-in-place concrete bridge decks, or emergency repair of broken cracks in cement concrete pavement slabs.