A rapid repairing material for local damage of small box girder of road and a preparation method thereof

Abstract

The application discloses a kind of quick repair materials of local damage of road small box girder and preparation method thereof, belong to road engineering material field.The material is composed of powder component A and liquid component B;Powder component A includes heavy-burning magnesium oxide, metakaolin, active zinc oxide, wollastonite powder, sodium fluorosilicate, borax pentahydrate and potassium dihydrogen phosphate, liquid component B includes water and sodium citrate;Preparation method uses step-by-step process, first sodium fluorosilicate, borax and metakaolin are premixed, then main mixing is carried out with other raw materials.The application utilizes reaction heat release to promote the release of fluoride ion, quickly excites metakaolin to generate composite gel, cooperates with the water resistance modification of zinc oxide and the interface enhancement effect of wollastonite, solves the problem of poor water resistance and weak interface bonding force of traditional material, has the characteristics of quick setting, high early strength, good water resistance and firm interface bonding.

Description

Technical Field

[0001] This invention relates to the field of road box girder repair technology, specifically to a rapid repair material for localized damage to road box girders and its preparation method. Background Technology

[0002] As crucial load-bearing components of bridges and elevated roads, small box girders are prone to localized damage such as potholes and exposed rebar under repeated vehicle dynamic loads and environmental erosion. To ensure smooth traffic flow, repair materials are typically required to have rapid setting and hardening properties and high early strength, enabling immediate reopening after repair. Magnesium phosphate cement-based materials, due to their excellent rapid-hardening and early-strength characteristics, have become the preferred material for such emergency repair projects.

[0003] However, the hydration product of conventional magnesium phosphate cement, potassium magnesium phosphate hexahydrate, tends to dissolve or undergo crystal structure transformation in an aqueous environment, resulting in poor long-term water resistance and a significant decline in strength after immersion in water. Existing technologies typically improve water resistance by adding metal oxides such as zinc oxide or incorporating mineral admixtures. However, zinc oxide has a significant retarding effect in magnesium phosphate systems. Increasing the zinc oxide content to achieve high water resistance leads to excessively prolonged slurry setting time and severely weakens the early strength of the material, making the repaired pavement unable to withstand traffic loads in the short term. Simultaneously, commonly used mineral admixtures, such as metakaolin, have low reactivity in the absence of effective activation, making it difficult to play a filling and reinforcing role in the early stages of hydration.

[0004] Furthermore, the quality of the interfacial bonding between the repair material and the old concrete matrix directly determines the durability of the repair layer. Ordinary magnesium phosphate cement is acidic or neutral, and its connection with the alkaline silicate concrete matrix relies mainly on physical interlocking, lacking sufficient chemical bonding at the interface. Under the unique vibration environment of small box girders, this simple physical bonding is prone to failure, leading to interfacial peeling or detachment of the repair layer and causing secondary damage. Existing technologies struggle to simultaneously ensure high water resistance, high early strength, and excellent interfacial bonding performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a rapid repair material for localized damage to road box girders and its preparation method. The aim is to solve the problems of reduced early strength, prolonged setting time, and insufficient interfacial bonding strength with old concrete matrix caused by the introduction of high zinc oxide content into existing magnesium phosphate cement-based repair materials to improve water resistance.

[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a rapid repair material for localized damage to road box girders: The material is packaged in two components, consisting of powder component A and liquid component B. The powder component A is made from the following raw materials in parts by weight: 100 parts of calcined magnesium oxide, 20-25 parts of metakaolin, 12-15 parts of active zinc oxide, 6-8 parts of wollastonite powder, 3-4 parts of sodium fluorosilicate, 6-8 parts of borax pentahydrate, and 65-75 parts of potassium dihydrogen phosphate. The liquid component B is made from the following raw materials in parts by weight: 40-45 parts water and 1.5 parts sodium citrate; When in use, the mass ratio of liquid component B to powder component A is 0.18:1 to 0.21:1.

[0007] By adopting the above technical solution, this invention utilizes the thermo-chemical synergistic effect between the components to ensure the material's water resistance while also considering its early strength and interfacial properties. Its mechanism of action is as follows: After the powder and liquid are mixed, potassium dihydrogen phosphate dissolves and undergoes an exothermic acid-base reaction with recalcined magnesium oxide, causing the slurry temperature to rise. This temperature increase promotes the hydrolysis of sodium fluorosilicate, generating hydrogen and fluoride ions. Because sodium fluorosilicate and metakaolin are in close contact beforehand, the highly reactive fluoride ions, aided by the thermal environment, break the silicon-aluminum-oxygen bonds on the metakaolin surface, causing its layered structure to depolymerize and release active aluminum and silicon ions. These active ions rapidly complex with magnesium and phosphate ions in the system, forming an amorphous magnesium-aluminum-phosphorus-silicon composite gel. This gel fills the gap in the early stages of hydration. Filling the spaces between magnesium oxide particles and magnesium phosphate crystals compensates for the early structural voids caused by the retarding effect of zinc oxide, giving the material high early strength. As hydration proceeds, active zinc oxide reacts with phosphate ions to form insoluble zinc phosphate hydrates on the surface of magnesium phosphate hydration products. Combined with the aforementioned dense composite gel, this blocks the channels for water to dissolve the crystals. In addition, wollastonite powder releases calcium ions in the acidic liquid phase, generating calcium phosphate precipitates and CSH gels in the interface transition zone between the repair material and the old concrete matrix, achieving chemical bonding and thus improving the interfacial adhesion strength.

[0008] Preferably, the powder component A is made from the following raw materials in parts by weight: 100 parts of calcined magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate; the liquid component B is made from the following raw materials in parts by weight: 40 parts of water and 1.5 parts of sodium citrate.

[0009] By adopting the above technical solution, the stoichiometric ratio of the acid-base reaction is optimized, ensuring that magnesium oxide and zinc oxide react fully, while controlling the setting time within an appropriate range to meet the requirements of rapid repair projects.

[0010] Preferably, the active zinc oxide has a specific surface area ≥ 45 m². 2 / g of nano- or submicron-sized zinc oxide; the recalcined magnesium oxide has a magnesium oxide content of ≥90% and has been calcined at a high temperature of above 1500℃.

[0011] By adopting the above technical solutions, the high specific surface area of ​​active zinc oxide improves its coverage efficiency on the surface of hydration products; the high-temperature calcined recalcined magnesium oxide reduces the initial reaction rate, prevents excessively rapid solidification, and ensures the volume stability in the later stage.

[0012] Preferably, in the powder component A, the metakaolin, sodium fluorosilicate and borax pentahydrate exist in the form of a premixed modified body, wherein the sodium fluorosilicate and borax pentahydrate are adsorbed on the surface of the metakaolin particles.

[0013] By adopting the above technical solution, the mass transfer distance between the activator and the activated material is shortened by adsorption. At the moment of hydration exothermic reaction, the local high concentration of fluoride ions directly acts on metakaolin, which improves the reaction conversion rate and the timeliness of activation, and avoids the hysteresis effect caused by long-distance ion diffusion.

[0014] Secondly, the present invention provides a method for preparing a rapid repair material for localized damage to road box girders: The method includes the following steps: S1. Preparation of powder component A: First, premixing is carried out: the prescribed amounts of sodium fluorosilicate, borax pentahydrate and metakaolin are put into the first mixing equipment for mixing, so that the catalyst components are adsorbed on the surface of metakaolin to obtain the premixed material. Then, the main mixing is carried out: the premixed material is added together with the formulated amounts of calcined magnesium oxide, active zinc oxide, wollastonite powder and potassium dihydrogen phosphate into the second mixing equipment for mixing until it is evenly dispersed, and then sealed and packaged to obtain powder component A. S2. Preparation of liquid component B: Under stirring, add the prescribed amount of sodium citrate to the prescribed amount of water, stir until completely dissolved, and seal and store to obtain liquid component B; S3. On-site slurry preparation: The liquid component B and the powder component A are mixed in proportion and stirred evenly to obtain the repair slurry.

[0015] By employing the above technical solution, this method uses a stepwise mixing process to control the spatial distribution of micro-components. Compared to one-time mixing, the premixing process ensures that sodium fluorosilicate preferentially adsorbs onto the surface of metakaolin, avoiding its random dispersion in the large amount of magnesium oxide and potassium dihydrogen phosphate matrix, which would reduce the contact probability. This spatial proximity ensures that within the window period during which zinc oxide exerts its retarding effect, metakaolin can be promptly activated to form a gel that fills the pores, thereby ensuring the stability of the material properties.

[0016] Preferably, in step S1, the premixing is carried out in a V-type mixer with a controlled rotation speed of 15-20 r / min and a mixing time of 10-15 minutes; the main mixing is carried out in a double-helix conical mixer with a controlled rotation speed of 40-60 r / min and a mixing time of 20-30 minutes, and the coefficient of variation (CV) of the mixed powder is controlled to be less than 5%.

[0017] By adopting the above technical solutions, the low-speed V-type mixer utilizes the convection principle to achieve uniform loading of additives on the surface of ultrafine powders, while reducing dust. The double-helix conical mixer utilizes a combination of rotation and revolution to achieve uniform dispersion of heavy magnesium oxide and light metakaolin with significant density differences, and the low coefficient of variation ensures the quality consistency between product batches.

[0018] Preferably, in step S3, the stirring is carried out using high-speed shear stirring, with a stirring speed of 800-1200 r / min and a stirring time of 90-120 seconds.

[0019] By adopting the above technical solution, high-speed shear stirring can destroy the liquid film resistance on the surface of powder particles, accelerate the penetration of water molecules, adapt to the characteristics of high solid content and fast reaction speed of this system, and enable the slurry to reach a suitable rheological state in a short time.

[0020] This invention provides a rapid repair material for locally damaged road box girders and its preparation method. It has the following beneficial effects: 1. This invention constructs a premixed system of sodium fluorosilicate and metakaolin, utilizing the heat of reaction in the early stage of magnesium phosphate cement hydration to promote the release of fluoride ions, rapidly stimulating the metakaolin to form a magnesium-aluminum-phosphorus-silicon composite gel. This gel fills the matrix pores in the early stage, effectively offsetting the weakening effect of the retarding effect of active zinc oxide on early strength; combined with the protective layer of insoluble zinc phosphate hydrate formed by the reaction of zinc oxide and phosphate in the later stage, the repair material maintains a compressive strength of ≥30MPa after 1 hour while achieving a water softening coefficient of ≥1.0, solving the problem of traditional magnesium phosphate repair materials struggling to balance early strength and water resistance.

[0021] 2. This invention introduces wollastonite powder as a modifying component, utilizing its slight solubility under acidic conditions to release calcium ions. Calcium ions accumulate in the interface transition zone between the repair material and the old concrete, and react with phosphate ions and hydration products on the matrix surface to generate calcium-containing phosphates and CSH gel, increasing the chemical bonding force in the interface region, significantly improving the interfacial shear bond strength between the repair material and the matrix, and reducing the risk of re-peeling after repair.

[0022] 3. This invention employs a stepwise preparation process combining premixing and primary mixing to ensure that sodium fluorosilicate preferentially adsorbs onto the surface of metakaolin particles. This specific microscopic distribution shortens the diffusion distance between the catalytic components and the reaction substrate, ensuring that metakaolin can be timely and fully activated within the specific window period of hydration exothermic reaction. This avoids reaction lag or performance fluctuations caused by random dispersion of components, ensuring the consistency of product quality in batch production. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method for preparing road box girder repair material according to the present invention. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see the appendix Figure 1 This invention provides a rapid repair material for localized damage to road box girders and its preparation method. The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products: Calcined magnesium oxide (MgO): CAS No. 1309-48-4, obtained by calcining magnesite at 1550℃, with a purity ≥92.5%, active calcium oxide content ≤1.5%, average particle size D50 of 40μm, and specific surface area of ​​320m². 2 / kg, citric acid neutralization time CAC is 240s; Metakaolin: CAS No. 92704-41-1, is kaolin produced by suspension calcination at 750℃, with an average particle size D50 of 8μm, active alumina content ≥43%, and active silica content ≥52%; Activated zinc oxide: chemical formula ZnO, CAS number 1314-13-2, produced by indirect method, purity ≥99.7%, specific surface area 45m². 2 / g; Wollastonite powder: chemical formula CaSiO3, CAS number 13983-17-0, in the form of needle-like crystalline powder, aspect ratio 12:1, passing through a 325 mesh sieve with a pass rate ≥98%; Potassium dihydrogen phosphate: chemical formula KH2PO4, CAS number 7778-77-0, industrial grade 1, purity ≥98.5%, powder fineness all passes through a 60-mesh sieve; Sodium fluorosilicate: Chemical formula Na₂SiF₆, CAS number 16893-85-9, purity ≥99.0%; Borax pentahydrate: Chemical formula Na₂B₄O₇˙₅H₂O, CAS No. 12179-04-3, residue on 200-mesh sieve ≤1.0%; Sodium citrate: Chemical formula C6H5Na3O7˙2H2O, CAS No. 6132-04-3, analytical grade.

[0026] Preparation Example 1: This preparation example provides a method for preparing a rapid repair material for localized damage to road box girders, corresponding to the formulation of Example 1 (modified process: potassium dihydrogen phosphate is adjusted to a powder component), including the following steps: (1) Preparation of powder component A: Weigh the raw materials according to the proportions in Example 1. First, construct a “catalyst-activation premix system” by adding sodium fluorosilicate (3 parts), borax pentahydrate (8 parts), and metakaolin (22 parts) in the formula into a V-type mixer and premixing for 12 minutes at a speed of 18 r / min to allow the catalyst to be fully adsorbed on the surface of the metakaolin. The obtained premix was then added together with calcined magnesium oxide (100 parts), active zinc oxide (14 parts), wollastonite powder (8 parts) and potassium dihydrogen phosphate (65 parts) into a double helix conical mixer and mixed at 50 r / min for 25 minutes until all components were evenly dispersed (coefficient of variation CV < 5%). The mixture was then sealed in a moisture-proof bag to obtain powder component A.

[0027] (2) Preparation of liquid component B: Add the prescribed amount of water to the acid-resistant reactor, turn on the stirrer (400 r / min), add sodium citrate, stir until completely dissolved, and seal for storage.

[0028] (3) On-site mixing: Mix liquid component B and powder component A in proportion, and use an electric mixer to stir for 100 seconds at a speed of 1000 r / min to obtain the repair slurry.

[0029] Preparation Example 2: This preparation example provides a method for preparing a rapid repair material for localized damage to road box girders, corresponding to the formulation in subsequent Example 2 (high zinc oxide, low reaction rate formulation), using the lower limit of the process parameter range, and including the following steps: (1) Preparation of powder component A: Weigh the raw materials according to the proportions in Example 2. Add sodium fluorosilicate (3 parts), borax pentahydrate (8 parts) and metakaolin (20 parts) into a V-type mixer and premix for 10 minutes at a speed of 15 r / min; then add calcined magnesium oxide (100 parts), active zinc oxide (15 parts), wollastonite powder (8 parts) and potassium dihydrogen phosphate (65 parts), and mix in a double helical conical mixer at a speed of 40 r / min for 20 minutes until the mixture is uniform, and then seal and package.

[0030] (2) Preparation of liquid component B: Sodium citrate (1.5 parts) is dissolved in water (40 parts) at room temperature, and stirred at 300 r / min until completely dissolved. Then it is sealed and stored.

[0031] (3) On-site mixing: Mix liquid component B and powder component A at a mass ratio of 0.19:1, and use an electric mixer to stir for 90 seconds at a speed of 800 r / min to obtain the repair slurry.

[0032] Preparation Example 3: This preparation example provides a method for preparing a rapid repair material for localized damage to road box girders, corresponding to the formulation in subsequent Example 3 (high metakaolin, high activation energy formulation), using the upper limit of the process parameter range, and including the following steps: (1) Preparation of powder component A: Weigh the raw materials according to the proportions in Example 3. Add sodium fluorosilicate (4 parts), borax pentahydrate (8 parts) and metakaolin (25 parts) into a V-type mixer and premix for 15 minutes at a speed of 20 r / min; then add calcined magnesium oxide (100 parts), active zinc oxide (12 parts), wollastonite powder (8 parts) and potassium dihydrogen phosphate (65 parts), and mix in a double helical conical mixer at a speed of 60 r / min for 30 minutes to ensure the uniformity of the powder, and then seal and package.

[0033] (2) Preparation of liquid component B: Sodium citrate (1.5 parts) is dissolved in water (40 parts) at room temperature, and stirred at 500 r / min until completely dissolved. Then it is sealed and stored.

[0034] (3) On-site mixing: Mix liquid component B and powder component A at a mass ratio of 0.18:1 (i.e. 41.5:222), and use an electric mixer to stir for 120 seconds at a speed of 1200r / min to obtain the repair slurry. Example 1:

[0035] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method, using an optimal intermediate value for the raw material ratio, and includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of reburned magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate.

[0036] First, weighed sodium fluorosilicate, borax pentahydrate and metakaolin are placed in a V-type mixer, the speed is set to 18 r / min and the mixing time is 12 minutes to obtain a premix. Subsequently, the above premixed material, along with calcined magnesium oxide, activated zinc oxide, wollastonite powder, and potassium dihydrogen phosphate, was fed into a double-helix conical mixer. The speed was set to 50 r / min, and the mixing time was 25 minutes, until the materials were mixed evenly (coefficient of variation CV < 5%). After passing the test, the mixture was sealed and packaged to obtain powder component A.

[0037] (2) Preparation of liquid component B: Weigh out 40 parts water and 1.5 parts sodium citrate by weight.

[0038] Add the weighed water to the mixing tank, turn on the mixer (400 r / min), add sodium citrate, and stir at room temperature until completely dissolved to form a clear and transparent liquid, which is liquid component B.

[0039] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.189:1 (i.e., 41.5 parts liquid to 220 parts powder). Using a handheld electric mixer, the mixture is stirred at a high speed of 1000 r / min for 100 seconds. When the slurry temperature rises slightly and exhibits a thixotropic fluid state, stirring is stopped immediately to obtain the repair material. Example 2:

[0040] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method. It employs high zinc oxide content and relatively low process parameters (lower limit of the range) to verify performance under extreme water resistance design, and includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of calcined magnesium oxide, 20 parts of metakaolin, 15 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate.

[0041] First, weighed sodium fluorosilicate, borax pentahydrate and metakaolin are placed in a V-type mixer, the speed is set to 15 r / min and the mixing time is 10 minutes to obtain a premix. Subsequently, the above premixed material, along with calcined magnesium oxide, active zinc oxide, wollastonite powder, and potassium dihydrogen phosphate, were fed into a double-helix conical mixer. The speed was set to 40 r / min, and the mixing time was 20 minutes, until the materials were evenly mixed. The mixture was then sealed and packaged to obtain powder component A.

[0042] (2) Preparation of liquid component B: Weigh out 40 parts water and 1.5 parts sodium citrate by weight.

[0043] Add the weighed water to the mixing tank, turn on the mixer (300 r / min), add sodium citrate, and stir until completely dissolved to obtain liquid component B.

[0044] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.189:1 (i.e., 41.5 parts liquid to 219 parts powder). The mixture is stirred for 90 seconds at 800 rpm using an electric mixer to obtain the repair material. Example 3:

[0045] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method. It employs a high kaolin content and relatively high process parameters (upper limit of the range) to verify the performance of the reinforced gel network and under high excitation energy. The method includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of calcined magnesium oxide, 25 parts of metakaolin, 12 parts of active zinc oxide, 8 parts of wollastonite powder, 4 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate.

[0046] First, weighed sodium fluorosilicate, borax pentahydrate and metakaolin are placed in a V-type mixer, the speed is set to 20 r / min and the mixing time is 15 minutes to obtain a premix. Subsequently, the above premixed material, along with calcined magnesium oxide, active zinc oxide, wollastonite powder, and potassium dihydrogen phosphate, were fed into a double-helix conical mixer. The speed was set to 60 r / min, and the mixing time was 30 minutes, until the materials were evenly mixed. The mixture was then sealed and packaged to obtain powder component A.

[0047] (2) Preparation of liquid component B: Weigh out 40 parts water and 1.5 parts sodium citrate by weight.

[0048] Add the weighed water to the mixing tank, turn on the mixer (500 r / min), add sodium citrate, and stir until completely dissolved to obtain liquid component B.

[0049] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.187:1 (i.e., 41.5 parts liquid to 222 parts powder). The mixture is stirred for 120 seconds using an electric mixer at 1200 rpm to obtain the repair material. Example 4:

[0050] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method. The ratio of potassium dihydrogen phosphate to water is adjusted to create a high-acidity activation environment. The method includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of calcined magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 75 parts of potassium dihydrogen phosphate.

[0051] The preparation process is the same as in Example 1, namely: premixing (18 r / min, 12 minutes) followed by main mixing (50 r / min, 25 minutes) to obtain powder component A.

[0052] (2) Preparation of liquid component B: Weigh out 45 parts water and 1.5 parts sodium citrate by weight.

[0053] The preparation process is the same as in Example 1, thus obtaining liquid component B.

[0054] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.202:1 (i.e., 46.5 parts liquid to 230 parts powder). The mixing process is the same as in Example 1, thus obtaining the repair material. Example 5:

[0055] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method. It employs a low amount of retarder to simulate a rapid-setting formulation under low-temperature conditions, and includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of calcined magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 6 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate.

[0056] The preparation process is the same as in Example 1, and powder component A is obtained.

[0057] (2) Preparation of liquid component B: Weigh out 40 parts water and 1.5 parts sodium citrate by weight.

[0058] The preparation process is the same as in Example 1, thus obtaining liquid component B.

[0059] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.190:1 (i.e., 41.5 parts liquid to 218 parts powder). The mixing process is the same as in Example 1, thus obtaining the repair material. Example 6:

[0060] This embodiment provides a rapid repair material for localized damage to road box girders and its preparation method. A low wollastonite content is used to verify the minimum effective amount of the interface component. The method includes the following steps: (1) Preparation of powder component A: Weigh out 100 parts by weight of calcined magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 6 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate.

[0061] The preparation process is the same as in Example 1, and powder component A is obtained.

[0062] (2) Preparation of liquid component B: Weigh out 40 parts water and 1.5 parts sodium citrate by weight.

[0063] The preparation process is the same as in Example 1, thus obtaining liquid component B.

[0064] (3) Preparation of on-site repair grout: Liquid component B and powder component A are mixed at a mass ratio of 0.190:1 (i.e., 41.5 parts liquid to 218 parts powder). The mixing process is the same as in Example 1, thus obtaining the repair material.

[0065] Comparative Example 1: This comparative example provides a conventional magnesium phosphate repair material as a blank control.

[0066] Compared with Example 1, the difference is that metakaolin, active zinc oxide, wollastonite powder and sodium fluorosilicate were not added to powder component A, while the other components and preparation process are the same.

[0067] Comparative Example 2: This comparative example provides a repair material containing only high levels of zinc oxide but lacking a synergistic activation mechanism, aiming to verify the negative impact of adding zinc oxide alone on early strength.

[0068] Compared with Example 1, the difference is that metakaolin and sodium fluorosilicate were not added to powder component A, while the other components and preparation process are the same.

[0069] Comparative Example 3: This comparative example provides a repair material lacking a chemical activator, aiming to verify the key inductive role of sodium fluorosilicate in a thermally activated system.

[0070] Compared with Example 1, the difference is that sodium fluorosilicate was not added to powder component A, while the other components and preparation process are the same.

[0071] Comparative Example 4: This comparative example provides a repair material lacking interfacial chemical bonding components, aiming to verify the contribution of wollastonite powder to interfacial adhesion performance.

[0072] Compared with Example 1, the difference is that no wollastonite powder was added to powder component A, while the other components and preparation process are the same.

[0073] Comparative Example 5: This comparative example provides a repair material with a normalized acid-base ratio (low acidity) to verify the impact of the "acid starvation" phenomenon on material performance under a high-filling-content alkaline system.

[0074] Compared with Example 1, the difference is that the amount of potassium dihydrogen phosphate in powder component A is reduced to 40 parts (making the M / P molar ratio about 8:1, which is the recommended ratio for conventional magnesium phosphate cement), while the other components and preparation process are the same.

[0075] Test Example 1: 1. Experiment Description All tests were conducted at a temperature of 20±2℃ and a relative humidity of 50±5%. After preparing each group of slurries according to the aforementioned proportions and processes, the setting time was determined using a Vicat apparatus in accordance with GB / T1346 standard. The initial setting time was recorded from the time water was added and stirring until the test needle sank to a distance of 4mm±1mm from the bottom plate of the neat slurry, and the final setting time was recorded as the time when the test needle sank to a distance of 0.5mm. The compressive strength test was conducted according to GB / T17671 standard, using a 40mm×40mm×160mm triple steel mold. Due to the rapid hardening of the material, it was cast in one go and manually tamped and compacted, then leveled. Specimens for 1-hour strength were demolded 45 minutes after casting, while specimens for 1-day and 28-day strength were demolded 1 hour after casting. After demolding, they were left to cure naturally in air. The test was conducted using a fully automatic pressure testing machine, with the loading rate controlled at 2400 N / s ± 200 N / s, and the arithmetic mean of the three specimens was taken.

[0076] 2. Test Results Table 1. Test results of basic physical and mechanical properties of the examples and comparative examples

[0077] 3. Results Analysis and Conclusions Table 1 shows that the initial setting times of Examples 1 to 6 ranged from 14 to 23 minutes, and the final setting times ranged from 21 to 34 minutes. Compared with Comparative Example 2 (initial setting time of 58 minutes) which only added zinc oxide, the setting time of the Example groups was significantly shortened under the same zinc oxide content. Zinc oxide usually adsorbs on the surface of magnesium oxide, hindering hydration and resulting in delayed setting. However, the data from the Example groups indicate that sodium fluorosilicate in the system promoted the dissolution of aluminum ions in metakaolin under exothermic reaction conditions. The gelling products generated by aluminum ions participating in the reaction accelerated the hardening of the slurry, offsetting the retarding effect of zinc oxide. In Example 4, increasing the amount of potassium dihydrogen phosphate further shortened the initial setting time to 14 minutes, indicating that the increased reactant concentration accelerated the dissolution and protonation of magnesium oxide. In terms of strength, the 1-hour compressive strength of Example 1 was 33.4 MPa, while that of Comparative Example 3 (without sodium fluorosilicate) was only 24.8 MPa. Both contained metakaolinite, and the difference in strength confirmed the activating effect of fluoride ions on the activity of metakaolinite. In the absence of fluoride ion attack, metakaolinite mainly played a physical filling role in the early stage; in the presence of fluoride ions, it participated in the construction of the early gel network. The 1-hour strength of Comparative Example 2 (containing only zinc oxide) was only 8.4 MPa, indicating that single zinc oxide modification would significantly reduce early strength, and it is necessary to combine it with aluminosilicate components to simultaneously meet the requirements of durability and early strength. Comparative Example 5 simulated the acid-base ratio of conventional magnesium phosphate cement (M / P molar ratio approximately 8:1), and its 1-hour and 28-day strengths were 12.3 MPa and 46.4 MPa, respectively, significantly lower than those of Example 1. This result reflects the acid consumption competition within the system. After introducing acid-consuming components such as zinc oxide and wollastonite, maintaining the conventional low acid ratio would lead to phosphate depletion and incomplete reaction. Examples 1 to 6, by increasing the acid ratio, ensured the reaction driving force of each component, thereby forming a dense structure.

[0078] Test Example 2: 1. Experiment Description This test case primarily examines the bonding ability between the repair material and the substrate, as well as its stability under harsh environments. First, the interfacial bond strength was tested using the oblique shear test method, referring to JC / T2381 and ASTM C882 standards. A pre-prepared C50 ordinary silicate concrete specimen (75mm×75mm×75mm) was used as the substrate. After curing for 28 days, it was cut at a 30° angle, and the cut surface was manually roughened and dust removed. Half of the substrate was placed at the bottom of a 75mm×75mm×150mm mold, and the prepared repair grout was poured and compacted. After the specimen was naturally cured indoors for 28 days, a pressure testing machine was used to load it at a rate of 1500 N / s. The failure load was recorded, and the interfacial shear bond strength was calculated. Next, the water resistance (softening coefficient) was determined according to GB / T50082 standard. Six 40mm×40mm×160mm specimens were prepared for each group and naturally cured for 3 days. Three of these specimens were then naturally cured in air for 28 days to determine their dry compressive strength; the other three were completely immersed in water at 20±2℃ for 28 days, then removed, wiped dry, and their water immersion compressive strength was determined. The ratio of water immersion strength to dry strength was calculated as the softening coefficient. Finally, the resistance to chloride ion penetration was determined using the electric flux method. Cylindrical specimens with a diameter of 100 mm and a height of 50 mm were prepared and naturally cured for 28 days before undergoing vacuum saturation. The specimens were then installed between the two electrodes of the measuring instrument. A 3.0% NaCl solution was injected into the negative electrode tank, and a 0.3 mol / L NaOH solution was injected into the positive electrode tank. A 60V DC voltage was applied, and the total charge passing through the specimen over 6 hours was recorded.

[0079] 2. Test Results Table 2. Durability and interface performance test data of the examples and comparative examples

[0080] 3. Results Analysis and Conclusions Table 2 shows that the interfacial bond strength of Examples 1 to 5 ranged from 6.4 to 7.3 MPa, with the failure surface mainly located inside the old concrete matrix. The bond strength of Comparative Example 4, without added wollastonite, was only 2.9 MPa, indicating that wollastonite plays a major role in improving interfacial bond strength. Wollastonite releases calcium ions in an acidic environment, reacting with phosphate ions and matrix surface products to form calcium-containing phosphates and CSH gel, forming chemical bonds. In Example 6, the strength decreased to 5.9 MPa after reducing the amount of wollastonite, further confirming the positive correlation between dosage and strength. Comparative Example 1, relying solely on physical interlocking, had the lowest bond strength. Regarding water resistance, Comparative Example 1 had a softening coefficient of 0.82, indicating a decrease in strength after immersion in water. This is attributed to the tendency of potassium magnesium phosphate hexahydrate crystals to dissolve in water. The softening coefficients of the Example groups were all greater than 1.0, indicating a continuous increase in strength in water. Example 2 had the highest coefficient of 1.09, because the sparingly soluble zinc phosphate hydrate formed by zinc oxide covered the crystal surface, while the aluminosilicate gel formed by fluoride-activated metakaolin filled the pores, blocking water erosion. Comparative Example 3, although containing metakaolin, lacked sodium fluorosilicate activation, resulting in insufficient gel formation and a water resistance coefficient of only 0.88. Electrical flux tests showed that the values ​​in the example groups were all below 400°C, belonging to the extremely low permeability level, while Comparative Example 1 reached as high as 1280°C. Comparative Example 5, due to insufficient acid leading to incomplete reaction, had higher porosity and an electrical flux of 890°C. The example groups, by adjusting the acid-base ratio and introducing ultrafine powders such as metakaolin and zinc oxide, utilized the product filling effect to reduce pore connectivity and inhibit chloride ion migration.

Claims

1. A rapid repair material for localized damage to road box girders, characterized in that, The material is packaged in two components, consisting of powder component A and liquid component B. The powder component A is made from the following raw materials in parts by weight: 100 parts of calcined magnesium oxide, 20-25 parts of metakaolin, 12-15 parts of active zinc oxide, 6-8 parts of wollastonite powder, 3-4 parts of sodium fluorosilicate, 6-8 parts of borax pentahydrate, and 65-75 parts of potassium dihydrogen phosphate. The liquid component B is made from the following raw materials in parts by weight: 40-45 parts water and 1.5 parts sodium citrate; When in use, the mass ratio of liquid component B to powder component A is 0.18:1 to 0.21:

1.

2. The rapid repair material for partial damage to road box girders according to claim 1, characterized in that, The powder component A is made from the following raw materials in parts by weight: 100 parts of calcined magnesium oxide, 22 parts of metakaolin, 14 parts of active zinc oxide, 8 parts of wollastonite powder, 3 parts of sodium fluorosilicate, 8 parts of borax pentahydrate, and 65 parts of potassium dihydrogen phosphate; the liquid component B is made from the following raw materials in parts by weight: 40 parts of water and 1.5 parts of sodium citrate.

3. The rapid repair material for partial damage to road box girders according to claim 1, characterized in that, The active zinc oxide has a specific surface area ≥ 45m². 2 / g of nano- or submicron-sized zinc oxide; the recalcined magnesium oxide has a magnesium oxide content of ≥90% and has been calcined at a high temperature of above 1500℃.

4. The rapid repair material for partial damage to road box girders according to claim 1, characterized in that, In the powder component A, metakaolin, sodium fluorosilicate and borax pentahydrate exist in the form of a premixed modified body, wherein sodium fluorosilicate and borax pentahydrate are adsorbed on the surface of metakaolin particles.

5. The rapid repair material for partial damage to road box girders according to any one of claims 1 to 4, characterized in that, The initial setting time of the material is 14-23 minutes, the compressive strength after 1 hour is ≥30MPa, and the water softening coefficient is ≥1.

0.

6. A method for preparing a rapid repair material for locally damaged road box girders as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of powder component A: First, premixing is carried out: the prescribed amounts of sodium fluorosilicate, borax pentahydrate and metakaolin are put into the first mixing equipment for mixing, so that the catalyst components are adsorbed on the surface of metakaolin to obtain the premixed material. Then, the main mixing is carried out: the premixed material is added together with the formulated amounts of calcined magnesium oxide, active zinc oxide, wollastonite powder and potassium dihydrogen phosphate into the second mixing equipment for mixing until it is evenly dispersed, and then sealed and packaged to obtain powder component A. S2. Preparation of liquid component B: Under stirring, add the prescribed amount of sodium citrate to the prescribed amount of water, stir until completely dissolved, and seal and store to obtain liquid component B; S3. On-site slurry preparation: The liquid component B and the powder component A are mixed in proportion and stirred evenly to obtain the repair slurry.

7. The preparation method according to claim 6, characterized in that, In step S1, the premixing is carried out in a V-type mixer, with the rotation speed controlled at 15-20 r / min and the mixing time at 10-15 minutes.

8. The preparation method according to claim 6, characterized in that, In step S1, the main mixing is carried out in a double-helix conical mixer, with the rotation speed controlled at 40-60 r / min, the mixing time at 20-30 minutes, and the coefficient of variation (CV) of the mixed powder controlled at <5%.

9. The preparation method according to claim 6, characterized in that, In step S2, the stirring speed is 300-500 r / min and the stirring is carried out at room temperature.

10. The preparation method according to claim 6, characterized in that, In step S3, the stirring is carried out using high-speed shear stirring, with a stirring speed of 800-1200 r / min and a stirring time of 90-120 seconds.

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