High-performance magnesium phosphate cement-based material for rapidly repairing cement concrete pavement and preparation method of high-performance magnesium phosphate cement-based material

Abstract

The invention provides a high-performance magnesium phosphate cement-based material for rapidly repairing a cement concrete pavement and a preparation method of the high-performance magnesium phosphate cement-based material, and belongs to the technical field of inorganic cementing materials. According to the invention, multiple components such as dead burned magnesium oxide, potassium dihydrogen phosphate, borax, nano silicon dioxide, a graphene / multi-walled carbon nanotube composite reinforcing agent, a phase change temperature control microcapsule, a double-cavity self-healing microcapsule, an intelligent interfacial activity regulating agent, an SBR emulsion and basalt fiber are cooperatively designed; the problems that traditional MPC is too fast in temperature rise, poor in interface bonding, insufficient in toughness and lack of self-healing and functionalization are solved. The material can be rapidly constructed and develop high strength in an environment of-10 DEG C to 50 DEG C, and is suitable for high-requirement rapid repair scenes of projects such as roads, bridges and airports.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic cementitious materials, and particularly relates to a high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement and a preparation method thereof. BACKGROUND

[0002] Magnesium phosphate cement (MPC) is an inorganic cementitious material with fast hardening, high strength, low shrinkage and good bonding performance, which is generated by the reaction of magnesium oxide (MgO) and phosphate. In recent years, MPC has been widely used in the field of cement concrete repair. However, MPC has the following problems: the heat release of hydration is concentrated, the temperature rise rate is high, and the high temperature gradient can induce early microcracks; the toughness is insufficient and lacks self-healing ability, the material is brittle, and after the crack expands, it cannot be blocked; the wettability of the old concrete base is poor, and the interface bonding is insufficient, which leads to easy interface delamination, limiting its application in the interface repair of high dynamic load and complex structure, the fatigue load bearing capacity of the interface combination structure after repair is limited; there is no temperature regulation function and damage sensing ability, which is difficult to meet the requirements of intelligent operation and maintenance; and the adaptability to cold environment is poor, and the hydration rate decreases significantly in low temperature environment.

[0003] Although the prior art attempts to improve the performance of the MPC system by adding fibers, retarders, and additives, it is still difficult to solve the problems of temperature control, self-healing, interface toughening, and intelligent monitoring. Therefore, there is an urgent need for a new high-performance MPC material with multiple intelligent regulation performance to realize rapid, durable and intelligent repair of road engineering. SUMMARY

[0004] The present application relates to the technical field of inorganic cementitious materials, and particularly relates to a high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement and a preparation method thereof.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application provides a high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement, which comprises the following components in mass fraction: dead burned magnesium oxide 100-130 parts; potassium dihydrogen phosphate 45-65 parts; borax 5-12 parts; nanosilica 3-6 parts; graphene / multi-walled carbon nanotube composite reinforcing agent 0.05-0.3 parts; phase change temperature control microcapsule 2-6 parts; double-cavity self-healing microcapsule 1-3 parts; intelligent interface active control agent 0.3-1.0 parts; butadiene-styrene copolymer emulsion 8-12 parts; Basalt fiber 0.5~2 parts; Water 28~58 parts.

[0006] Further, the graphene / multi-walled carbon nanotube composite reinforcing agent is obtained by ultrasonic dispersion and carboxyl modification treatment of graphene and MWCNT.

[0007] Further, the phase change temperature control microcapsule is prepared by in-situ polymerization with hexadecanol or paraffin as the core and urea-formaldehyde resin or gelatin-arabic gum composite wall material as the coating material. The phase change temperature of the phase change temperature control microcapsule is 25~35℃.

[0008] Further, the double-cavity self-healing microcapsule encapsulates Na2HPO4 solution and ultrafine MgO powder in the double cavities, respectively.

[0009] Further, the intelligent interfacial activity regulator contains a silane group and a phosphate group bifunctional structure, and forms a bridging layer with the old concrete surface and MKP crystals.

[0010] Further, the nano-silicon dioxide has a particle size of 5~10 nm and a purity of ≥99.5%; The heavy-burned magnesium oxide is obtained by grinding magnesite calcined at a high temperature of 1500~1800℃, and the purity of the heavy-burned magnesium oxide is ≥90%.

[0011] Further, the fiber contains basalt fiber, and the length of the fiber is 10~15 mm and the diameter is 15~20 μm. The butadiene-styrene copolymer emulsion is a German BASF ECO7623, milky white, with a solid content of 50.6%.

[0012] The application also provides a preparation method of the high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement. 1) A mixture A is obtained by mixing heavy-burned magnesium oxide, potassium dihydrogen phosphate, borax, nano-silicon dioxide and basalt fiber in proportion. 2) After mixing water and the mixture A, the water temperature is controlled at 15~25°C, and butadiene-styrene copolymer emulsion is added for continuous mixing to obtain a mixture B.

[0013] 3) The graphene / multi-walled carbon nanotube composite reinforcing agent, the interfacial activity regulator, the phase change temperature control microcapsule and the double-cavity self-healing microcapsule are sequentially added to the mixture B and stirred uniformly to obtain a mixture C, which is the high-performance magnesium phosphate cement-based material.

[0014] Further, in the step 1), the rotating speed of mixing is 100-150 r / min, and the mixing time is 1-5 min.

[0015] Further, in the step 2), the rotating speed of mixing of water and the mixture A is 100-150 r / min, and the mixing time is 1-5 min; and the mixing is continued for 1-2 min.

[0016] The beneficial effects of the present application are as follows: The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement provided by the present application realizes the comprehensive performance such as fast hardening, high strength, wide temperature range construction, crack resistance, toughening, high adhesion, self-healing and intelligent monitoring which cannot be realized by traditional MPC through the synergistic construction of six functional modules of phase change temperature adjustment, self-healing microcapsule, interface activation, nano enhancement, electric conduction sensing and multi-scale toughening. The phase change temperature control microcapsule (PCM-MgO) introduced in the present application utilizes the phase change latent heat absorption and release to realize the active adjustment of MPC hydration heat release: inhibits the hydration peak temperature and slows down the heat rising rate; makes the early hydration in high temperature environment not too intense, prevents the heat-induced microcracks; releases the phase change heat in low temperature environment, makes up for the lack of external temperature, and ensures the normal hydration. Therefore, the material can remain stable condensation and hardening in a wide temperature range of-10 DEG C to 50 DEG C, which is a technical effect that cannot be realized by traditional MPC system.

[0017] The present application adopts double-cavity structure microcapsule to encapsulate Na2HPO4 and MgO respectively, which automatically ruptures and releases the contents when cracks occur: generates new crystals in situ on the crack surface, fills the cracks; blocks the further expansion of the cracks; improves the impermeability, freeze-thaw resistance and long-term durability of the material. The self-healing mechanism can greatly reduce the frequency of secondary repair, significantly prolong the service life of the structure, and realize the functional self-repairing ability which traditional MPC system does not have.

[0018] The present application introduces an interface active regulator containing silane group and phosphoric acid group, which can simultaneously form chemical bond with old concrete and MKP hydration products: form a double bond complex bridge layer of "Si-O-Si + P-O-Mg"; significantly improve the interface bonding strength, which can reach ≥6 MPa; avoid common failure modes such as delamination, warping and bulging of the repair layer. The dual-functional interface bridging technology breaks through the inherent defect of MPC that it is not suitable for old concrete, and realizes the long-term stable combination of the repair layer and the base layer.

[0019] The application adopts a nano-SiO2 and graphene / MWCNT composite system to synergistically build a reinforcing and conductive network: the nano-SiO2 fills pores, promotes MKP crystal nucleation, generates M-S-H gel, and improves strength and compactness; the carbon-based nanomaterial forms a continuous flexible conductive channel, improving toughness and electrical response; the resistance of the slurry and hardened body changes with the generation of microcracks, realizing intelligent sensing of structural damage. Through nanostructure reinforcement + conductive network, the application not only improves the mechanical properties, but also endows the material with monitorability, realizing intelligent road operation and maintenance.

[0020] Through the synergistic effect of the SBR emulsion and basalt fibers, the MPC material is changed from a brittle system to a high-toughness composite structure: the SBR forms a flexible film phase, improving deformation capacity and reducing shrinkage cracking; the basalt fibers build a three-dimensional bridging network, inhibiting crack initiation and propagation; the crack width is reduced by 40-60%, and the material failure mode is changed from brittle fracture to ductile failure. The toughening system significantly improves the service stability of the material under complex working conditions such as traffic load and temperature difference cycles. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A preparation flowchart of the high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement of the application; Figure 2 An interface SEM image of the composite material obtained after curing of Example 5 of the application; Figure 3 An interface SEM image of the composite material obtained after curing of Comparative Example 1 of the application. DETAILED DESCRIPTION

[0022] The application provides a high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement, which comprises the following components in mass fraction: Dead burned magnesium oxide 100-130 parts; Potassium dihydrogen phosphate 45-65 parts; Borax 5-12 parts; Nanosilica 3-6 parts; Graphene / multi-walled carbon nanotube composite reinforcing agent 0.05-0.3 parts; Phase change temperature control microcapsule 2-6 parts; Double-cavity self-healing microcapsule 1-3 parts; Intelligent interface active control agent 0.3-1.0 parts; Butadiene-styrene copolymer emulsion 8-12 parts; Basalt fiber 0.5-2 parts; Water 28-58 parts.

[0023] In this invention, the content of the recalcined magnesium oxide is preferably 100-120 parts by mass, and more preferably 115 parts by mass.

[0024] In this invention, the content of potassium dihydrogen phosphate is preferably 55-65 parts by mass, and more preferably 60 parts.

[0025] In this invention, the content of borax is preferably 6-12 parts by mass, more preferably 8-10 parts. The borax is chemically analytical grade sodium tetraborate pentahydrate Na₂B₄O₇·5H₂O.

[0026] In this invention, the content of the nano-silica is preferably 4.5 to 5.5 parts by mass, and more preferably 5 parts.

[0027] In this invention, the content of the butadiene-styrene copolymer emulsion, by weight, is preferably 10-11 parts, more preferably 10.5 parts. The butadiene-styrene copolymer emulsion is from BASF Styrofan (Germany). ® ECO7623 is milky white with a solid content of 50.6%.

[0028] In this invention, the content of basalt fiber is preferably 0.6 to 1.5 parts by mass, and more preferably 1 to 1.2 parts by mass.

[0029] In this invention, the water content is preferably 33 to 45 parts by mass, and more preferably 35 to 40 parts by mass.

[0030] In this invention, the particle size of the nano-silica is 5~10nm, preferably 7nm; the purity is ≥99.5%, preferably ≥99.9%.

[0031] In this invention, the recalcined magnesium oxide is obtained by grinding magnesite after calcination at a high temperature of 1500~1800℃, preferably after calcination at a high temperature of 1700℃; the purity of the recalcined magnesium oxide is ≥90%, preferably ≥92%.

[0032] In this invention, the length of the basalt fiber is 10-15 mm, preferably 12 mm; the diameter is 15-20 μm, preferably 17.4 μm.

[0033] In this invention, the graphene / multi-walled carbon nanotube (MWCNT) composite reinforcing agent is a graphene-MWCNT composite material that has undergone ultrasonic dispersion and carboxylation modification, with a dosage of 0.05-0.3 parts, preferably 0.1-0.3 parts, and more preferably 0.3 parts. This composite reinforcing agent forms a three-dimensional conductive network in the MPC, which can be used for resistance monitoring and damage sensing of microcracks. Simultaneously, it improves the material's microstructure, enhances flexural toughness and interfacial adhesion, effectively fills the pores of hydration products and forms a bridging structure, thus slowing crack propagation.

[0034] In this invention, the intelligent interfacial activity regulator is a bifunctional molecule containing silane and phosphate groups, with a dosage of 0.3-1.0 parts, preferably 0.5-1.0 parts, and more preferably 1 part. This regulator can adsorb onto the surface of MgO and the aggregate interface during hydration, achieving efficient wetting and bonding of cement paste and aggregate through interfacial energy regulation. Simultaneously, it can promote the nucleation of nano-SiO2 and MgO hydration products, improving matrix density and interfacial bonding strength.

[0035] In this invention, the phase change temperature-controlled microcapsules are prepared by in-situ polymerization, with cetyl alcohol or paraffin as the core and urea-formaldehyde resin or gelatin-gum arabic composite wall material as the coating material. The phase change temperature of the microcapsules is 25~35°C, and the dosage is 2~6 parts, preferably 3~6 parts, and more preferably 6 parts. The microcapsules adhere to the surface of MgO particles to form a PCM-MgO structure, releasing or absorbing heat during temperature fluctuations to achieve adaptive temperature control. This allows them to absorb thermal stress during material hardening and transportation, aiding in interfacial bonding and structural stability, reducing the risk of early cracking, and improving the material's adaptability to construction and maintenance.

[0036] In this invention, the dual-cavity self-healing microcapsules have a dual-cavity wall structure, encapsulating Na2HPO4 and MgO components respectively, with a dosage of 1-3 parts, preferably 2-3 parts, and more preferably 3 parts. When microcracks occur in the matrix, the microcapsules rupture, releasing the active components and undergoing a secondary hydration reaction, thereby achieving the material's self-healing function, effectively delaying crack propagation, and improving the material's long-term durability and structural integrity. Synergistically, with graphene / MWCNT and SBR emulsions, it can enhance the toughness of the composite interface layer, achieving multi-scale toughening and interface repair.

[0037] This invention also provides a method for preparing the above-mentioned high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavements, comprising the following steps: 1) Weigh out and mix the recalcined magnesium oxide, potassium dihydrogen phosphate, borax, nano silica and basalt fiber in proportion to obtain mixture A; 2) After mixing water and mixture A, the water temperature is controlled at 15~25°C. Butadiene-styrene copolymer emulsion is added and mixing is continued to obtain mixture B.

[0038] 3) Add graphene / multi-walled carbon nanotube composite reinforcing agent, interfacial activity regulator, phase change temperature-controlled microcapsule and dual-cavity self-healing microcapsule to mixture B in sequence and stir evenly to obtain mixture C, which is the high-performance magnesium phosphate cement-based material.

[0039] In this invention, in step 1), the mixing speed is 100~150 r / min and the mixing time is 1~5 min.

[0040] In this invention, in step 2), the mixing speed of water and mixture A is 100~150 r / min, preferably 120 r / min; the mixing time is 1~5 min, preferably 1~3 min; and the mixing continues for 1~2 min, preferably 1~1.5 min.

[0041] In this invention, the obtained high-performance magnesium phosphate cement-based material is cast and molded and then placed in the laboratory for air curing. After 30 minutes, the mold is removed and air curing continues until the corresponding age before relevant performance tests are conducted. The air curing temperature is 20±2℃ and the air humidity is 70±5%.

[0042] In summary, the material of this invention, through the synergistic construction of five functional modules and a multi-scale structure, possesses multiple performance advantages, including high strength, high toughness, high durability, intelligence, and rapid construction. It can fully meet the requirements of rapid road repair and intelligent operation and maintenance, demonstrating outstanding technological innovation value and broad engineering application prospects. Firstly, the reaction kinetics are controllable, achieving the optimal construction time window. By combining the retarding effects of borax, the induction of nano-SiO2 crystal nuclei, and the phase delay of the SBR emulsion film on the MPC hydration system, the material's setting speed is transformed from the traditional "too fast, difficult to construct" to "controllable, stable, and moderate." The initial setting time can be adjusted to 8-15 minutes, significantly increasing the construction operation time. The hydration reaction heat peak is reduced and delayed, avoiding early cracking induced by thermal stress. The MPC system maintains its high strength characteristics for 1 hour, meeting the engineering requirements for rapid traffic reopening. This controllable kinetic characteristic effectively improves the material's adaptability in complex construction environments. Secondly, the dual effects of nanofilling and chemical reaction construct ultra-dense microstructured nano-SiO2. Through a triple mechanism of "interstitial filling—crystallization—reaction," the microstructure of the material is deeply regulated: 7nm-level particle size effectively fills the interstitial pores of MKP crystals, reducing the proportion of interconnected pores; it induces uniform nucleation of hydration products, resulting in more regular and dense crystals; and it reacts with Mg... 2+The reaction forms an M–S–H gel, enhancing the intercrystalline bonding strength. This synergistic effect significantly reduces the material's porosity, resulting in a denser microstructure, significantly improved compressive and flexural strength, and a fundamental improvement in durability. Then, polymer flexibility and interfacial reinforcement enhance the system's crack and fatigue resistance. The flexible continuous film structure formed by the SBR emulsion, combined with the MPC crystal framework, significantly improves the material's toughness: increasing strain capacity, transforming material failure from "brittle fracture" to "ductile failure"; reducing plastic shrinkage and hydration shrinkage, making stress concentration less likely to lead to cracks; and significantly enhancing the chemical-mechanical bonding between the repair layer and the old concrete interface. This flexible control mechanism ensures that the material maintains good crack resistance even under adverse conditions such as temperature differences and repeated loading. Fourth, a three-dimensional fiber bridging network constructs a high-toughness and long-life repair layer. Basalt fibers form a three-dimensional distribution network in the matrix, effectively inhibiting crack propagation through a "pull-deflection-passivation" mechanism: microcracks can be bridged at the initiation stage, significantly reducing crack size; crack propagation paths are deflected, improving energy dissipation capacity; the maximum crack width can be reduced by 40-60%, adapting to repeated traffic loads. This makes the material more stable and reliable under fatigue, impact, and complex load conditions. The repair material of this invention has highly balanced comprehensive performance, suitable for rapid, heavy-load, and long-term service scenarios. The material of this invention achieves overall improvement in strength, toughness, workability, and durability, meeting the stringent requirements of key projects such as roads, bridges, and airport runways, enabling rapid traffic restoration; the bond strength with the old concrete interface is significantly increased, reducing the risk of later delamination; it has excellent freeze-thaw resistance, salt corrosion resistance, and wear resistance, with outstanding long-term durability. This highly synergistic material characteristic realizes a qualitative leap in rapid repair materials from "fast but fragile" to "fast and highly durable."

[0043] In summary, this invention, through multi-level regulation from the nanoscale to macroscopic mechanics, comprehensively improves the reaction rate, strength, toughness, durability, and interfacial properties of MPC repair materials, solving the core pain points of traditional rapid repair materials such as "high strength but brittleness, rapid hardening but cracking, and insufficient bonding," demonstrating significant theoretical innovation value and engineering application advantages. This invention provides a high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavements and its preparation method. By optimizing the phosphate system and adjusting the Mg / P ratio, the material achieves a compressive strength of ≥30 MPa in 3 hours and a strength exceeding 65 MPa after 28 days, significantly higher than traditional MPC or OPC materials. Simultaneously, the flexural strength reaches 9 MPa after 1 day, exhibiting excellent rigid-toughness bonding characteristics; the interfacial bonding strength with aged concrete reaches 4 MPa, far exceeding traditional repair mortar (<1.5 MPa); fracture toughness is improved by over 60%, significantly enhancing crack resistance, and possessing both emergency repair and long-term service capabilities. It controls the hydration heat release process and the development of internal stress, significantly inhibits early drying shrinkage cracks, and the setting time can be adjusted to 30 minutes. It is suitable for emergency repair construction in various climatic environments and can realize the process of "pre-mixed bagged + rapid on-site water addition and mixing", which greatly improves construction efficiency and meets the needs of emergency repair scenarios (such as emergency repair of highways and airport pavements at night).

[0044] The key technological advancements and innovations compared to existing technologies are summarized in Table 1 below: Table 1 Performance Comparison

[0045] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] For emergency repair of early-stage cracks and potholes in highway pavements, the components and dosages used in this embodiment are as follows: 120 parts of recalcined magnesium oxide, 60 parts of potassium dihydrogen phosphate, 10 parts of borax, 3 parts of nano-silica, and 0.6 parts of basalt fiber were weighed and mixed to obtain mixture A. 30 parts of water were mixed with mixture A, and the water temperature was controlled at 25°C. 10 parts of butadiene-styrene copolymer emulsion were added and mixing continued to obtain mixture B. Subsequently, 0.1 parts of graphene / MWCNT, 0.5 parts of interfacial activity modifier, 3 parts of phase change temperature-controlled microcapsules, and 2 parts of dual-cavity self-healing microcapsules were added one by one and stirred until homogeneous to obtain mixture C.

[0048] After the mixture is stirred evenly, it is poured and molded for 30 minutes, then demolded and placed on a specimen rack for air curing. The air curing temperature is 20±2 ℃ and the air humidity is 70±5%.

[0049] Example 2

[0050] The development of a high-toughness MPC reinforcement material for bridge expansion joints, as described in this embodiment, includes the following components and dosages: 110 parts of recalcined magnesium oxide, 50 parts of potassium dihydrogen phosphate, 12 parts of borax, 5 parts of nano-silica, and 0.2 parts of basalt fiber were weighed and mixed to obtain mixture A. 40 parts of water were mixed with mixture A, and the water temperature was controlled at 25°C. 10 parts of butadiene-styrene copolymer emulsion were added and mixing continued to obtain mixture B. Subsequently, 0.2 parts of graphene / MWCNT, 0.6 parts of interfacial activity modifier, 4 parts of phase change temperature-controlled microcapsules, and 2 parts of dual-cavity self-healing microcapsules were added one by one and stirred until homogeneous to obtain mixture C.

[0051] After the mixture is stirred evenly, it is poured and molded for 30 minutes, then demolded and placed on a specimen rack for air curing. The air curing temperature is 20±2 ℃ and the air humidity is 70±5%.

[0052] Example 3

[0053] The MPC composite material used in this embodiment for repairing holes and improving anti-slip properties of municipal sidewalks has the following components and dosages: 120 parts of recalcined magnesium oxide, 50 parts of potassium dihydrogen phosphate, 12 parts of borax, 4 parts of nano-silica, and 0.5 parts of basalt fiber were weighed and mixed to obtain mixture A. 40 parts of water were mixed with mixture A, and the water temperature was controlled at 25°C. 12 parts of butadiene-styrene copolymer emulsion were added and mixing continued to obtain mixture B. Subsequently, 0.15 parts of graphene / MWCNT, 0.7 parts of interfacial activity modifier, 3 parts of phase change temperature-controlled microcapsules, and 1.5 parts of dual-cavity self-healing microcapsules were added one by one and stirred until homogeneous to obtain mixture C.

[0054] After the mixture is stirred evenly, it is poured and molded for 30 minutes, then demolded and placed on a specimen rack for air curing. The air curing temperature is 20±2 ℃ and the air humidity is 70±5%.

[0055] Example 4

[0056] 100 parts of recalcined magnesium oxide, 65 parts of potassium dihydrogen phosphate, 12 parts of borax, 4 parts of nano-silica, and 1 part of basalt fiber were weighed and mixed to obtain mixture A. 40 parts of water were mixed with mixture A, and the water temperature was controlled at 25°C. 9 parts of butadiene-styrene copolymer emulsion were added and mixing continued to obtain mixture B. Subsequently, 0.25 parts of graphene / MWCNT, 0.8 parts of interfacial activity modifier, 5 parts of phase change temperature-controlled microcapsules, and 2.5 parts of dual-cavity self-healing microcapsules were added one by one and stirred until homogeneous to obtain mixture C.

[0057] After the mixture is stirred evenly, it is poured and molded for 30 minutes, then demolded and placed on a specimen rack for air curing. The air curing temperature is 20±2 ℃ and the air humidity is 70±5%.

[0058] Example 5

[0059] Weigh out 130 parts of recalcined magnesium oxide, 55 parts of potassium dihydrogen phosphate, 10 parts of borax, 6 parts of nano-silica, and 2 parts of basalt fiber, and mix them to obtain mixture A. Mix 40 parts of water with mixture A, control the water temperature at 25°C, add 12 parts of butadiene-styrene copolymer emulsion and continue mixing to obtain mixture B. Subsequently, add 0.3 parts of graphene / MWCNT, 1 part of interfacial activity regulator, 6 parts of phase change temperature-controlled microcapsules, and 3 parts of dual-cavity self-healing microcapsules one by one, and stir evenly to obtain mixture C.

[0060] After the mixture is stirred evenly, it is poured and molded for 30 minutes, then demolded and placed on a specimen rack for air curing. The air curing temperature is 20±2 ℃ and the air humidity is 70±5%.

[0061] Figure 2 The image shows an SEM image of the interface of the composite material after curing in Example 5. It can be seen that the pores in the magnesium phosphate cement are uniformly distributed, and the fibers are embedded in the matrix with good bonding performance. Nano-silica filling the pores makes the magnesium phosphate cement matrix more compact, and the polymer aggregates within the interface, enhancing the bond with cement concrete. Meanwhile, large cracks exist at the interface between the magnesium phosphate cement and ordinary silicate cement mortar, but almost none at the interface with coarse aggregate. This directly reflects that the magnesium phosphate cement formulation in Example 5 has a triple performance enhancement mechanism of "nanomaterial filling + fiber toughening + polymer reinforcement," giving it a more significant advantage in repairing cement concrete structures.

[0062] Comparative Example 1

[0063] Same as Example 5, except that SBR emulsion is not added.

[0064] Figure 3 This is a SEM image of the interface of the composite material after curing, as shown in the figure. It can be seen from the image that compared to... Figure 2 Numerous cracks exist at the interface between magnesium phosphate cement and cement concrete, and the magnesium phosphate cement matrix also contains many microcracks. This indicates that the polymer plays a significant role in enhancing the interfacial bonding performance. This further confirms the scientific validity and rationality of the proposed rapid repair scheme for enhanced magnesium phosphate cement in cement concrete structures.

[0065] Comparative Example 2

[0066] Same as Example 5, except that no basalt fiber is added.

[0067] Comparative Example 3

[0068] Similar to Example 5, except that ordinary lightly calcined magnesia (which is obtained by calcining magnesium hydroxide extracted from magnesite at 800°C) is used instead of heavy-calcined magnesia.

[0069] Comparative Example 4

[0070] Same as Example 5, except that no graphene / MWCNT composite reinforcing agent is added.

[0071] Comparative Example 5

[0072] Same as Example 5, except that phase change temperature control microcapsules are not added.

[0073] Comparative Example 6

[0074] Same as Example 5, except that no dual-chamber self-healing microcapsules are added.

[0075] Comparative Example 7

[0076] Same as Example 5, except for the presence of a surfactant regulator.

[0077] Performance testing

[0078] After demolding, the high-performance magnesium phosphate cement-based material samples used for rapid repair of cement concrete pavement were air-cured. The compressive strength of the magnesium phosphate cement samples was measured at 3 h and the flexural strength at 1 d, in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The interfacial bond strength at 1 d was tested in accordance with JCT 2537-2019 "Magnesium Phosphate Repair Mortar". The test results are shown in Table 2.

[0079] Table 2. Measurement results of mechanical properties of high-performance magnesium phosphate cement-based materials used for rapid repair of cement concrete pavements.

[0080] As shown in Table 2, this invention introduces a multi-scale control strategy into the traditional MPC system, including nano-SiO2, SBR, basalt fiber, graphene / MWCNT, phase change temperature-controlled microcapsules, dual-cavity self-healing microcapsules, and intelligent interfacial activity regulators, thereby significantly improving the early mechanical properties and interfacial adhesion of the material. In the examples, the 3-hour compressive strength ranged from 30.81 to 37.57 MPa, with Example 1 showing the highest (37.57 MPa), significantly higher than ordinary magnesium phosphate cement (35 MPa), indicating that the material of this invention can obtain sufficient load-bearing capacity in a short time under rapid repair conditions. Single-factor comparative analysis shows that the compressive strength of Comparative Example 1 (without SBR emulsion) is 36.19 MPa, slightly lower than that of Example 5, indicating that SBR emulsion mainly contributes to interfacial toughness and flexural strength, with a relatively limited impact on initial compressive strength. Comparative Example 2 (without basalt fiber) showed a decrease in compressive strength to 31.79 MPa, indicating that fibers can form bridging structures in the matrix, improving microcrack control and thus enhancing overall compressive strength. Comparative Example 3 (lightly calcined magnesia replacing calcined magnesia) showed a significant decrease in compressive strength to 27.54 MPa, demonstrating the key role of highly active calcined magnesia in rapid strength development. Comparative Examples 4-7 (without phase change microcapsules, graphene / MWCNT, self-healing microcapsules, and interfacial activity regulators) showed compressive strengths of 32.45, 31.12, 32.01, and 29.38 MPa, respectively. This indicates that the synergistic effect of nano-reinforcing agents and microcapsules also significantly promotes short-term compressive strength, but its effect is less than that of magnesia activity and fiber toughening. Example 5 showed the highest flexural strength, reaching 15.78 MPa, approximately 2.6 times higher than ordinary magnesium phosphate cement, demonstrating the significant advantages of the composite toughening system in bridging cracks and dispersing stress. Comparative analysis shows that the flexural strength of Comparative Example 1 (without SBR emulsion) decreased to 8.37 MPa, demonstrating the key role of polymer emulsion in enhancing interfacial toughness and mitigating brittle failure. The flexural strength of Comparative Example 2 (without fiber) decreased to 7.98 MPa, indicating that fiber is one of the main factors contributing to the improved flexural strength. The flexural strength of Comparative Example 3 (with lightly calcined MgO as a substitute) was only 6.71 MPa, further emphasizing the decisive influence of highly reactive MgO on hydration rate and early toughness. The flexural strengths of Comparative Examples 4-7 were 10.32, 11.06, 10.15, and 8.92 MPa, respectively, indicating that nano-reinforcing agents, microcapsules, and interfacial activity regulators can enhance flexural strength to some extent, but their individual effects are not as significant as those of fibers or emulsions.

[0081] Example 5 showed the highest interfacial bond strength, reaching 5.94 MPa, significantly higher than ordinary magnesium phosphate cement (2.5 MPa), indicating that the material of this invention can maintain excellent bonding performance with old concrete during long-term use. Comparative analysis showed that Comparative Example 1 (without SBR emulsion) had a bond strength of 3.98 MPa, a significant decrease, highlighting the role of the emulsion in forming a flexible composite interfacial layer. Comparative Example 2 (without fibers) had a bond strength of 4.31 MPa, slightly lower than Example 5, indicating that fibers also contribute to maintaining the overall stability of the interface. Comparative Example 3 (with lightly calcined magnesium oxide as a substitute) had a bond strength of 4.12 MPa, indicating that MgO activity affects interfacial bonding and density. The bond strengths of Comparative Examples 4-7 were 4.21, 4.08, 4.17, and 3.85 MPa, respectively, showing that nano-reinforcing agents and microcapsules have a certain effect on interfacial strengthening, but the effect of a single factor is limited, requiring synergistic action with SBR emulsion and fibers to achieve the highest level.

[0082] This invention achieves multiple optimizations in rapid strength development, enhanced interfacial adhesion, and improved toughness through a multi-scale synergistic design of "nano-SiO2 + SBR emulsion + basalt fiber + nano-reinforcing agent + microcapsule + intelligent interface regulator". Single-factor comparisons further validated the mechanisms of action of each functional component in compressive strength, flexural strength, and interfacial adhesion, providing a scientific basis for the system design of high-performance MPC materials. The overall performance of the material of this invention reaches the international advanced level, balancing rapid construction and long-term durability, and has broad engineering application and industrialization potential. The material system of this invention is suitable for emergency repair and structural reinforcement of critical parts such as cement concrete pavements, bridge expansion joints, and airport runways, exhibiting excellent mechanical properties and construction adaptability, especially in harsh environments with low temperature, humidity, and frequent traffic loads.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavements, characterized in that, The components include the following parts by mass: 100-130 parts of recalcined magnesium oxide; 45-65 parts of potassium dihydrogen phosphate; 5-12 parts of borax; 3-6 parts of nano-silica; 0.05~0.3 parts of graphene / multi-walled carbon nanotube composite reinforcing agent; 2-6 portions of phase change temperature control microcapsules; 1-3 portions of dual-cavity self-healing microcapsules; 0.3~1.0 parts of intelligent interface activity regulator; 8-12 parts of butadiene-styrene copolymer emulsion; Basalt fiber 0.5-2 parts; Water 28-58 parts.

2. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to claim 1, characterized in that, The graphene / multi-walled carbon nanotube composite reinforcing agent is obtained by ultrasonic dispersion and carboxyl modification of graphene and MWCNT.

3. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavements according to claim 1 or 2, characterized in that, The phase change temperature control microcapsules are prepared by in-situ polymerization with cetyl alcohol or paraffin as the core and urea-formaldehyde resin or gelatin-gum arabic composite wall material as the coating material. The phase change temperature of the phase change temperature control microcapsule is 25~35℃.

4. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to claim 3, characterized in that, The dual-cavity self-healing microcapsule contains Na2HPO4 solution and ultrafine MgO powder in its two cavities, respectively.

5. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to claim 1 or 4, characterized in that, The intelligent interface activity regulator contains a dual-functional structure of silane and phosphate groups, which forms a bridging layer with the old concrete surface and MKP crystals.

6. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to claim 5, characterized in that, The nano-silica has a particle size of 5~10 nm and a purity of ≥99.5%. The recalcined magnesium oxide is obtained by grinding magnesite after calcination at a high temperature of 1500~1800℃, and the purity of the recalcined magnesium oxide is ≥90%.

7. The high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to claim 1 or 6, characterized in that, The fiber comprises basalt fiber, the fiber having a length of 10-15 mm and a diameter of 15-20 μm; The butadiene-styrene copolymer emulsion is BASF Styrofan® ECO7623 from Germany, which is milky white and has a solid content of 50.6%.

8. The method for preparing the high-performance magnesium phosphate cement-based material for rapid repair of cement concrete pavement according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Weigh out and mix the recalcined magnesium oxide, potassium dihydrogen phosphate, borax, nano silica and basalt fiber in proportion to obtain mixture A; 2) After mixing water and mixture A, the water temperature is controlled at 15~25°C. Butadiene-styrene copolymer emulsion is added and mixing is continued to obtain mixture B; 3) Add graphene / multi-walled carbon nanotube composite reinforcing agent, interfacial activity regulator, phase change temperature-controlled microcapsule and dual-cavity self-healing microcapsule to mixture B in sequence and stir evenly to obtain mixture C, which is the high-performance magnesium phosphate cement-based material.

9. The preparation method according to claim 8, characterized in that, In step 1), the mixing speed is 100~150 r / min and the mixing time is 1~5 min.

10. The preparation method according to claim 9, characterized in that, In step 2), the mixing speed of water and mixture A is 100~150 r / min, and the mixing time is 1~5 min; continue mixing for 1~2 min.

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