A rapid repair mortar and a method for preparing the same

Abstract

The application discloses a kind of quick repair mortar and preparation method thereof, according to weight fraction, quick repair mortar raw materials include coating modified magnesium oxide 300-500 parts, phosphate 100-150 parts, setting regulator 0-50 parts, quartz sand 300-600 parts, finely ground admixture 60-100 parts, rheological agent 5-20 parts.Each powder is mixed uniformly, and a proper amount of mixing water is added to stir uniformly and can be used.The application can reduce the reactivity of magnesium oxide at a lower calcination temperature by surface coating modification of magnesium oxide particles, thereby prolonging the operable time of magnesium phosphate cement-based repair material, and forming an in-situ polymer modified layer on the surface of magnesium oxide particles, enhancing the bonding performance of magnesium phosphate gel with other powders and aggregates.In addition, the application can utilize red mud, nickel slag and other harmful solid waste as resources, and the aluminum phase and iron phase can react with phosphate to form new mineral phases, improving the mechanical and durability properties of magnesium phosphate materials.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a rapid repair mortar and its preparation method. Background Technology

[0002] Due to water erosion, chemical corrosion, natural carbonization, and freeze-thaw damage, hydraulic structures such as locks, sluices, and canals are prone to surface concrete pitting, damage, cracking, and spalling, affecting the safe operation and service life of the hydraulic structures. To reduce the adverse effects on the daily operation of hydraulic structures, it is often necessary to use rapid repair mortar to quickly repair concrete surface defects.

[0003] Magnesium phosphate cement has advantages such as ultra-early strength, high bond strength, and good crack resistance. Its strength can continue to develop under water curing conditions, making it a common material for rapid repair. However, magnesium phosphate reacts violently with acids and alkalis, and its rapid setting makes it difficult to meet construction requirements, thus hindering its widespread adoption. CN201910628482.8 provides a magnesium phosphate cement-based rapid repair material, prepared from solid components and water, with a mass ratio of solid components to water of 1:(0.18-0.30). The solid components include the following substances by mass percentage: 23%-35% magnesium oxide powder, 13%-22% potassium dihydrogen phosphate, 0-9% fly ash, 28%-32% quartz sand, 1% borax, 2% silica fume, and 0-11% limestone powder, with the sum of the mass percentages of each substance in the solid components being 100%. This magnesium phosphate cement-based rapid repair material can effectively improve the interfacial bonding performance between new and old concrete under relatively low temperature conditions. CN202011278335.1 discloses a magnesium phosphate-based repair material, composed of the following raw materials in weight percentages: 30%-50% magnesium phosphate cement, 5%-20% fly ash microspheres, 1%-6% modified polymer powder, 3%-6% retarder, 0.1%-1% water-retaining agent, 30%-50% graded sand, and the balance being water. By optimizing the ratio of reburned magnesium powder and potassium dihydrogen phosphate, and adding fly ash and polymer powder, the bonding strength of the material is improved, ensuring a firm bond with the original interface and enhancing durability. Simultaneously, the setting time and workability are adjusted through the retarder and water-retaining components, resulting in excellent construction performance.

[0004] It is evident that, to reduce reactivity, existing technologies generally employ overburned magnesium oxide calcined at temperatures above 1700℃, resulting in high raw material costs (including phosphates) and consequently, high repair mortar costs. Borax has a good retarding effect, but excessive dosage can severely affect the strength of the repair material. Therefore, there is a need to develop a rapid repair mortar with controllable setting time, fast hardening and early strength, and high economic efficiency. Summary of the Invention

[0005] To address the shortcomings of existing rapid repair materials, this invention provides a modified phosphate cement-based rapid repair mortar and its preparation method, which can be applied to the rapid repair and durability protection of surface defects in hydraulic concrete.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A rapid repair mortar, characterized in that, by weight, its raw materials include: 300-500 parts of coated modified magnesium oxide, 100-150 parts of phosphate, 0-50 parts of setting regulator, 300-600 parts of quartz sand, 60-100 parts of finely ground admixture, and 5-20 parts of rheology modifier.

[0008] The phosphates include potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate, with a purity of not less than 99% and a mass ratio of (35-45):(35-45):(10-30).

[0009] The quartz sand is 80-120 mesh quartz sand, and the rheology modifier is one of melamine and naphthalene-based water-reducing agents.

[0010] The setting agent comprises borax and aluminum sulfate in a mass ratio of (50-70):(30-50). The borax is borax decahydrate with a particle size of less than 0.15 mm, and the aluminum sulfate is a chemically pure reagent with a particle size of less than 0.1 mm.

[0011] The coated and modified magnesium oxide was prepared according to the following method:

[0012] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1000-1200℃ for 3-5 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0013] (2) Dissolve 5-10 parts of coating agent in 100 parts of solvent, add 5-10 parts of modifier to obtain a solution;

[0014] (3) Take 40-60 parts of modified magnesium oxide A and add it to the solution prepared in step (2). Stir for 3-5 minutes at a stirring rate of 20-40 r / min. Then, remove the solvent by vacuum distillation for 2-3 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0015] (4) Dissolve 5-10 parts of coating agent in 100 parts of solvent, add 5-10 parts of modifier, and then prepare a solution;

[0016] (5) Take 40-60 parts of modified magnesium oxide B and add it to the solution prepared in step (4). Stir for 3-5 minutes at a stirring rate of 20-40 r / min. Then remove the solvent by vacuum distillation and grind it to a particle size of less than 80 μm to obtain coated modified magnesium oxide.

[0017] In step (2) or step (4) of the preparation of the coated modified magnesium oxide, the coating agent is one of polylactic acid and polylactic acid-glycolic acid, the solvent is one of chloroform and acetone, the modifier includes VAE adhesive powder and borax decahydrate, and the mass ratio is (40-70):(30-60), the minimum film-forming temperature of the VAE adhesive powder is lower than 5°C, and the particle size of the borax decahydrate is less than 0.1 mm.

[0018] The finely ground admixture was prepared according to the following method:

[0019] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 6-8, then put it into an oven at 80-100℃ to dry for 3-5 hours and cool it naturally to obtain intermediate product 1;

[0020] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0021] The present invention also provides a method for preparing rapid repair mortar, characterized in that modified magnesium oxide, phosphate, setting regulator, quartz sand, finely ground admixture and rheology modifier are weighed and mixed evenly, and then mixed with water and stirred evenly before use. The ratio of the mixing water to the total mass of the powder materials is 0.08 to 0.10.

[0022] The beneficial effects that this invention can achieve are:

[0023] (1) Polylactic acid or polylactic-glycolic acid is used as the surface coating layer of magnesium oxide particles. A dense isolation layer is formed on the surface of magnesium oxide particles through two coating processes, which inhibits the dissolution process of magnesium oxide and plays a "slow-release" role. As the reaction time increases, the surface coating layer will gradually degrade and break down in the pore liquid, and the magnesium oxide particles will dissolve and undergo acid-base reaction upon contact with water. Conventional magnesium phosphate cement materials generally use overburned magnesium oxide calcined at above 1700℃. This invention delays the reaction rate between magnesium oxide and phosphate through coating modification, and reduces the calcination temperature of overburned magnesium oxide by more than 500℃ while meeting the requirement of a long setting time (greater than 20 min), thus saving energy consumption.

[0024] (2) The modifier and coating agent are co-soluble in the solvent. The VAE adhesive powder contained in the prepared coating layer can form an in-situ polymer modification layer on the surface of magnesium oxide particles. Compared with the method of adding adhesive powder to mortar powder, this improves the uniformity of adhesive powder dispersion and can directionally induce the formation of polymer film on the surface of magnesium oxide particles, thereby enhancing the bonding performance of magnesium phosphate hydration gel with other powders and aggregates. The borax contained in the coating layer can quickly react with Mg +2 It forms a complex and creates a protective film on the surface of magnesium oxide in situ, which hinders the dissolution and reaction of magnesium oxide. Compared with adding borax to mortar powder, it improves the formation efficiency of borax complex and the retarding effect, and further controls the setting time.

[0025] (3) By using different phosphates in a certain proportion, the exothermic process, flow properties, and pore structure of the hydrated cementitious material can be optimized, resulting in both ultra-early strength and high later-stage strength after hardening. The setting retarder is a compound of borax and aluminum sulfate in a certain proportion. Aluminum sulfate can delay the exothermic rate of phosphate cement hydration. The combined use of the two can not only extend the setting time of magnesium phosphate cement, but also avoid the disadvantage of excessive strength loss when using borax alone as a retarder.

[0026] (4) This invention enables the resource utilization of harmful solid wastes such as red mud and nickel slag. Red mud is a waste discharged after extracting Al2O3 from bauxite, and its main components are Al2O3, Fe2O3, SiO2, etc. Nickel slag is a silicon-aluminum solid waste generated during the smelting and purification of nickel-iron alloys, and its main components are SiO2, Al2O3, CaO, and MgO. The dumping of red mud and nickel slag not only occupies land but also pollutes the environment. By modifying and grinding red mud and nickel slag to activate their chemical activity, when used as an admixture in the magnesium phosphate cementing system, the aluminum phase reacts with phosphate to generate mineral phases such as AlPO4·xH2O and MgAl2O4, and the iron phase reacts with phosphate to produce mineral phases such as Fe3(PO4)2(OH)3. This enriches the types of hydration products in the magnesium phosphate cementing system, improves the mechanical and durability properties of magnesium phosphate materials, and reduces the cost of repair mortar, making it highly economical. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments.

[0028]

Example 1

[0029] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 300 parts coated modified magnesium oxide, 100 parts phosphate, 0 parts setting regulator, 300 parts quartz sand, 60 parts finely ground admixture, and 5 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.08 (water to total powder materials mass), add water, and stir evenly before use.

[0030] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 35:35:30, the quartz sand is 80-120 mesh quartz sand, and the rheology modifier is melamine.

[0031] The coated and modified magnesium oxide was prepared by the following method:

[0032] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1000℃ for 5 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0033] (2) Dissolve 5 parts of polylactic acid in 100 parts of chloroform, add 5 parts of modifier to obtain the first solution N; repeat the step (dissolve 5 parts of polylactic acid in 100 parts of chloroform, add 5 parts of modifier) ​​to obtain the second solution N; the modifier is prepared by mixing VAE adhesive powder and decahydrate borax in a mass ratio of 40:60; the minimum film-forming temperature of the VAE adhesive powder is lower than 5℃, and the particle size of the decahydrate borax is less than 0.1mm.

[0034] (3) Take 40 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 3 min at a stirring rate of 20 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0035] (4) Take 40 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 3 min at a stirring rate of 20 r / min. Then remove the solvent by vacuum distillation and grind it to a particle size of less than 80 μm to obtain coated modified magnesium oxide.

[0036] The finely ground admixture was prepared according to the following method:

[0037] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 6, then put it into an 80℃ oven to dry for 5 hours and cool it naturally to obtain intermediate product 1;

[0038] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0039]

Example 2

[0040] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 400 parts coated modified magnesium oxide, 100 parts phosphate, 10 parts setting regulator, 400 parts quartz sand, 80 parts finely ground admixture, and 10 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.08 (water to total powder materials mass), add water, and stir evenly before use.

[0041] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 40:40:20. The setting regulator is prepared by mixing borax decahydrate with a particle size of less than 0.15 mm and aluminum sulfate with a particle size of less than 0.1 mm in a mass ratio of 50:50. The quartz sand is 80-120 mesh quartz sand. The rheology modifier is a naphthalene-based water-reducing agent. The aluminum sulfate is a chemically pure reagent.

[0042] The coated and modified magnesium oxide was prepared by the following method:

[0043] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 3 hours, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0044] (2) Dissolve 10 parts of polylactic acid in 100 parts of chloroform, add 10 parts of modifier to obtain the first solution N; repeat the step (dissolve 10 parts of polylactic acid in 100 parts of chloroform, add 10 parts of modifier) ​​to obtain the second solution N; the modifier is prepared by mixing VAE adhesive powder and decahydrate borax in a mass ratio of 50:50; the minimum film-forming temperature of the VAE adhesive powder is lower than 5℃, and the particle size of the decahydrate borax is less than 0.1mm.

[0045] (3) Take 40 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 5 min at a stirring rate of 40 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0046] (4) Take 40 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 5 min at a stirring rate of 40 r / min. Then remove the solvent by vacuum distillation and grind it to a particle size of less than 80 μm to obtain coated modified magnesium oxide.

[0047] The finely ground admixture was prepared according to the following method:

[0048] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 8, then put it into an 80℃ oven to dry for 4 hours and cool it naturally to obtain intermediate product 1;

[0049] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0050]

Example 3

[0051] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 450 parts coated modified magnesium oxide, 150 parts phosphate, 20 parts setting regulator, 400 parts quartz sand, 80 parts finely ground admixture, and 15 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.09 (water to total powder materials mass), add water, and stir evenly before use.

[0052] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 45:45:10. The setting agent is prepared by mixing borax decahydrate with a particle size of less than 0.15 mm and aluminum sulfate with a particle size of less than 0.1 mm in a mass ratio of 70:30. The quartz sand is 80-120 mesh quartz sand. The rheology modifier is melamine. The aluminum sulfate is a chemically pure reagent.

[0053] The coated and modified magnesium oxide was prepared by the following method:

[0054] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0055] (2) Dissolve 5 parts of polylactic acid in 100 parts of acetone, add 5 parts of modifier to obtain the first solution N; repeat the step (dissolve 5 parts of polylactic acid in 100 parts of acetone, add 5 parts of modifier) ​​to obtain the second solution N; the modifier is prepared by mixing VAE adhesive powder and decahydrate borax at a mass ratio of 70:30; the minimum film-forming temperature of the VAE adhesive powder is lower than 5℃, and the particle size of the decahydrate borax is less than 0.1mm.

[0056] (3) Take 60 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 5 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0057] (4) Take 60 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 5 minutes at a stirring rate of 30 r / min. Then remove the solvent by vacuum distillation and grind it until the particle size is less than 80 μm to obtain coated modified magnesium oxide.

[0058] The finely ground admixture was prepared according to the following method:

[0059] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 7, then put it into a 100℃ oven to dry for 4 hours and cool it naturally to obtain intermediate product 1;

[0060] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0061]

Example 4

[0062] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 450 parts coated modified magnesium oxide, 120 parts phosphate, 30 parts setting regulator, 450 parts quartz sand, 70 parts finely ground admixture, and 15 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.10 (water to total powder materials mass), add water, and stir evenly before use.

[0063] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 45:45:10. The setting agent is prepared by mixing borax decahydrate with a particle size of less than 0.15 mm and aluminum sulfate with a particle size of less than 0.1 mm in a mass ratio of 60:40. The quartz sand is 80-120 mesh quartz sand. The rheology modifier is melamine. The aluminum sulfate is a chemically pure reagent.

[0064] The coated and modified magnesium oxide was prepared by the following method:

[0065] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1000℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0066] (2) Dissolve 5 parts of polylactic acid-glycolic acid in 100 parts of acetone, add 5 parts of modifier to obtain the first solution N; repeat the step (dissolve 5 parts of polylactic acid-glycolic acid in 100 parts of acetone, add 5 parts of modifier) ​​to obtain the second solution N. The modifier is prepared by mixing VAE adhesive powder and borax decahydrate in a mass ratio of 70:30. The minimum film-forming temperature of the VAE adhesive powder is lower than 5°C, and the particle size of the borax decahydrate is less than 0.1 mm.

[0067] (3) Take 40 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 5 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0068] (4) Take 40 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 5 minutes at a stirring rate of 30 r / min. Then remove the solvent by vacuum distillation and grind it until the particle size is less than 80 μm to obtain coated modified magnesium oxide.

[0069] The finely ground admixture was prepared according to the following method:

[0070] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 6, then put it into a 100℃ oven to dry for 4 hours and cool it naturally to obtain intermediate product 1;

[0071] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0072]

Example 5

[0073] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 400 parts coated modified magnesium oxide, 125 parts phosphate, 40 parts setting regulator, 550 parts quartz sand, 90 parts finely ground admixture, and 10 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.09 (water to total powder materials mass), add water, and stir evenly before use.

[0074] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 40:40:20. The setting agent is prepared by mixing borax decahydrate with a particle size of less than 0.15 mm and aluminum sulfate with a particle size of less than 0.1 mm in a mass ratio of 60:40. The quartz sand is 80-120 mesh quartz sand. The rheology modifier is melamine. The aluminum sulfate is a chemically pure reagent.

[0075] The coated and modified magnesium oxide was prepared by the following method:

[0076] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0077] (2) Dissolve 10 parts of polylactic acid-glycolic acid in 100 parts of chloroform, add 10 parts of modifier to obtain the first solution N; repeat the step (dissolve 10 parts of polylactic acid-glycolic acid in 100 parts of chloroform, add 10 parts of modifier) ​​to obtain the second solution N; the modifier is prepared by mixing VAE adhesive powder and borax decahydrate in a mass ratio of 60:40; the minimum film-forming temperature of the VAE adhesive powder is lower than 5℃, and the particle size of the borax decahydrate is less than 0.1mm.

[0078] (3) Take 40 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 3 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0079] (4) Take 40 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 3 min at a stirring rate of 30 r / min. Then remove the solvent by vacuum distillation and grind it to a particle size of less than 80 μm to obtain coated modified magnesium oxide.

[0080] The finely ground admixture was prepared according to the following method:

[0081] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 7, then put it into a 100℃ oven to dry for 4 hours and cool it naturally to obtain intermediate product 1;

[0082] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0083]

Example 6

[0084] The rapid repair mortar of this embodiment, by weight, comprises the following raw materials: 500 parts coated modified magnesium oxide, 150 parts phosphate, 50 parts setting regulator, 600 parts quartz sand, 100 parts finely ground admixture, and 20 parts rheology modifier. Weigh out all powder materials and mix them evenly. Weigh out mixing water at a ratio of 0.09 (water to total powder materials mass), add water, and stir evenly before use.

[0085] The phosphate is prepared by mixing potassium dihydrogen phosphate, ammonium dihydrogen phosphate and disodium hydrogen phosphate in a mass ratio of 40:40:20. The setting agent is prepared by mixing borax decahydrate with a particle size of less than 0.15 mm and aluminum sulfate with a particle size of less than 0.1 mm in a mass ratio of 65:35. The quartz sand is 80-120 mesh quartz sand. The rheology modifier is melamine. The aluminum sulfate is a chemically pure reagent.

[0086] The coated and modified magnesium oxide was prepared by the following method:

[0087] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0088] (2) Dissolve 10 parts of polylactic acid-glycolic acid in 100 parts of acetone, add 10 parts of modifier to obtain the first solution N; repeat the step (dissolve 10 parts of polylactic acid-glycolic acid in 100 parts of acetone, add 10 parts of modifier) ​​to obtain the second solution N. The modifier is prepared by mixing VAE adhesive powder and borax decahydrate in a mass ratio of 60:40. The minimum film-forming temperature of the VAE adhesive powder is lower than 5°C, and the particle size of the borax decahydrate is less than 0.1 mm.

[0089] (3) Take 60 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 3 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0090] (4) Take 60 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 3 min at a stirring rate of 30 r / min. Then remove the solvent by vacuum distillation and grind it to a particle size of less than 80 μm to obtain coated modified magnesium oxide.

[0091] The finely ground admixture was prepared according to the following method:

[0092] (1) Add dilute hydrochloric acid to the red mud to adjust its pH to 7, then put it into a 100℃ oven to dry for 4 hours and cool it naturally to obtain intermediate product 1;

[0093] (2) Mix intermediate product 1 with nickel slag at a mass ratio of 3:1 and grind until the particle size is less than 75μm.

[0094] Comparative Example 1

[0095] Comparative Example 1 is basically the same as Example 3 in terms of composition and preparation method, except that the coated modified magnesium oxide is replaced by an equal amount of overburned magnesium oxide.

[0096] Comparative Example 2

[0097] Comparative Example 2 is basically the same as Example 3 in terms of composition and preparation method, except that the phosphate is only ammonium dihydrogen phosphate.

[0098] Comparative Example 3

[0099] Comparative Example 3 has the same composition and preparation method as Example 3, except that the setting agent is only borax decahydrate.

[0100] Comparative Example 4

[0101] Comparative Example 4 is basically the same as Example 3 in composition and preparation method, except that no modifier is used in the preparation of the coated modified magnesium oxide. That is, the coated modified magnesium oxide is prepared according to the following method:

[0102] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0103] (2) Dissolve 5 parts of polylactic acid in 100 parts of acetone to obtain solution N; two portions of solution N need to be prepared.

[0104] (3) Take 60 parts of modified magnesium oxide A and add it to the first part of solution N. Stir for 5 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B.

[0105] (4) Take 60 parts of modified magnesium oxide B and add it to the second part of solution N. Stir for 5 minutes at a stirring rate of 30 r / min. Then remove the solvent by vacuum distillation and grind it until the particle size is less than 80 μm to obtain coated modified magnesium oxide.

[0106] Comparative Example 5

[0107] Comparative Example 5 is basically the same as Example 3 in composition and preparation method, except that: the coated modified magnesium oxide is only coated once during preparation, that is, the coated modified magnesium oxide is prepared according to the following method:

[0108] (1) Crush magnesite to 20-30 mm, calcine it in a high-temperature furnace at 1200℃ for 4 h, cool it naturally, and then grind it to a particle size of less than 80 μm to obtain modified magnesium oxide A;

[0109] (2) Dissolve 5 parts of polylactic acid in 100 parts of acetone, add 5 parts of modifier to obtain solution N; the modifier is prepared by mixing VAE adhesive powder and borax decahydrate in a mass ratio of 70:30.

[0110] (3) Take 60 parts of modified magnesium oxide A and add it to solution N. Stir for 5 min at a stirring rate of 30 r / min. Then, remove the solvent by vacuum distillation for 2 hours and grind it until the particle size is less than 80 μm to obtain coated modified magnesium oxide.

[0111] Comparative Example 6

[0112] Comparative Example 6 is basically the same as Example 3 in composition and preparation method, except that the finely ground admixture is only nickel slag, that is, the finely ground admixture is prepared according to the following method:

[0113] (1) Grind the nickel slag until the particle size is less than 75 μm to obtain the desired particle size.

[0114] The rapid repair mortars of Examples 1-6 and Comparative Examples 1-6 were tested for fluidity, setting time, workability, compressive strength at 3 hours and 28 days, interfacial flexural strength at 3 hours and 28 days, and impact and abrasion resistance at 28 days. The results are shown in Table 1.

[0115] Flowability: The flowability of mortar is tested in accordance with GB / T2419-2005 "Method for Determination of Flowability of Cement Mortar".

[0116] Setting time: The setting time of the mortar is tested according to "8 Setting Time Test" in JGJ / T70-2009 "Basic Performance Test Methods for Building Mortar".

[0117] Workable time: Refer to the workability evaluation method in GB18445-2012 "Cement-based penetrating crystalline waterproof materials" to prepare a standard concrete slab. If the mortar cannot be properly applied and compacted on the standard concrete slab, it is considered to have no workability. The workable time is the time from the addition of water until the mortar loses its workability.

[0118] Compressive strength and interfacial flexural strength: tested according to JC / T 2381-2016 "Repair Mortar".

[0119] Impact and abrasion resistance: The test was conducted according to "5.21 Concrete impact and abrasion resistance test (underwater steel ball method)" in SL / T352-2020 "Test Procedure for Hydraulic Concrete", with a shaft rotation speed of 3000 r / min.

[0120] Table 1. Performance test results of each group of rapid repair mortar

[0121]

[0122]

[0123] As shown in Table 1, the rapid repair mortar provided by this invention has a long workable time, while also exhibiting ultra-early strength, high bond strength, and good impact and abrasion resistance. The setting time of each group of mortars in Examples 1-6 reached 20 minutes or even longer. Even without the addition of a setting regulator (Example 1), the workable time was 18 minutes. With the addition of a setting regulator, the workable time can be adjusted and extended as needed. The 3-hour compressive strength of each group of mortars was greater than 30 MPa, and the 3-hour interfacial flexural strength reached 4.5 MPa, indicating that the mortar has very high early strength, thus meeting the requirements for rapid repair. The 28-day compressive strength was above 80 MPa, and the impact and abrasion resistance was 14.5 h / (kg / m²). 2 The above indicates that the mortar has good long-term performance.

[0124] Compared with Example 3, Comparative Example 1 used conventional overburned magnesium oxide, which did not have the "slow-release" effect of coating modification. The magnesium oxide dissolved and reacted rapidly in the pore liquid, and the setting time and workable time were greatly shortened, which could not meet the construction requirements.

[0125] Compared with Example 3, Comparative Example 2 used only ammonium dihydrogen phosphate, which resulted in faster early strength development of the mortar, but reduced strength in the later stages. The 28-day compressive strength decreased by 25.3%, and the internal structure had more pores, affecting the later performance.

[0126] Compared with Example 3, the setting retarder in Comparative Example 3 was only borax decahydrate. Borax has a better retarding effect and the setting time is extended by 6 minutes, but it seriously affects the early (3h) and later (28d) strength of the mortar.

[0127] Compared with Example 3, no modifier was used in the preparation process of the coated modified magnesium oxide in Comparative Example 4. The borax in the coating layer lacked the effect of forming a protective film on the surface of magnesium oxide in situ. The setting time was shortened by 9 minutes, and the workable time was shortened. At the same time, due to the lack of the effect of forming an in situ polymer modification layer on the surface of magnesium oxide particles by VAE adhesive powder in the coating layer, the hydration gel performance of magnesium phosphate was reduced, and the interfacial flexural strength and impact abrasion resistance were reduced.

[0128] Compared with Example 3, the coating of modified magnesium oxide in Comparative Example 5 was carried out only once, the coating thickness was reduced, the content of modifier was also reduced, the setting time was shortened by 4 min, and the 28-day interfacial flexural strength and impact abrasion resistance were reduced.

[0129] Compared with Example 3, the finely ground admixture in Comparative Example 6 consisted only of nickel slag, with fewer new mineral phases formed by aluminum, iron and phosphate, resulting in reduced compressive strength, interfacial flexural strength and impact abrasion resistance.

[0130] Although the present invention has been described through embodiments, these embodiments are not intended to limit the invention. Those skilled in the art can make various modifications and alterations within the spirit of the invention, such as adjustments to component ratios or time ranges. The effects of such adjustments are predictable and therefore also fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined by the same or equivalent technical features in the claims of this application.

Claims

1. A rapid repair mortar, characterized in that, By weight, the raw materials include: 300-500 parts of coated modified magnesium oxide, 100-150 parts of phosphate, 0-50 parts of setting regulator, 300-600 parts of quartz sand, 60-100 parts of finely ground admixture, and 5-20 parts of rheology modifier. The phosphates include potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and disodium hydrogen phosphate, with a purity of not less than 99% and a mass ratio of (35~45):(35~45):(10~30); the quartz sand is 80~120 mesh quartz sand; and the rheology modifier is one of melamine and naphthalene-based water-reducing agent. The setting agent comprises borax and aluminum sulfate in a mass ratio of (50~70):(30~50), wherein the borax is borax decahydrate with a particle size of less than 0.15 mm, and the aluminum sulfate is a chemically pure reagent with a particle size of less than 0.1 mm. The coated and modified magnesium oxide was prepared according to the following method: Step 1: Crush magnesite to 20-30mm, calcine it in a high-temperature furnace at 1000-1200℃ for 3-5 hours, cool it naturally, and then grind it to a particle size of less than 80μm to obtain modified magnesium oxide A; Step 2: Dissolve 5-10 parts of the coating agent in 100 parts of solvent, add 5-10 parts of the modifier, and obtain a solution; Step 3: Take 40-60 parts of modified magnesium oxide A and add it to the solution prepared in Step 2. Stir for 3-5 minutes at a stirring rate of 20-40 r / min. Then, remove the solvent by vacuum distillation for 2-3 hours and grind it until the particle size is less than 80 μm to obtain modified magnesium oxide B. Step 4: Dissolve 5-10 parts of coating agent in 100 parts of solvent, add 5-10 parts of modifier, and then prepare a solution; Step 5: Take 40-60 parts of modified magnesium oxide B and add it to the solution prepared in Step 4. Stir for 3-5 minutes at a stirring rate of 20-40 r / min. Then remove the solvent by vacuum distillation and grind it until the particle size is less than 80 μm to obtain coated modified magnesium oxide. The coating agent is one of polylactic acid and polylactic acid-glycolic acid, the solvent is one of chloroform and acetone, and the modifier includes VAE adhesive powder and borax decahydrate, with a mass ratio of (40~70):(30~60). The minimum film-forming temperature of VAE adhesive powder is below 5℃, and the particle size of borax decahydrate is less than 0.1mm. The finely ground admixture was prepared according to the following method: Step 1: Add dilute hydrochloric acid to the red mud to adjust its pH to 6-8, then put it into an oven at 80-100℃ to dry for 3-5 hours, and let it cool naturally to obtain intermediate product 1; Step 2: Mix intermediate product 1 with nickel slag at a mass ratio of 3:1, and grind until the particle size is less than 75μm.

2. A method for the preparation of a rapid repair mortar according to claim 1, characterized in that, Weigh out the coated modified magnesium oxide, phosphate, setting regulator, quartz sand, finely ground admixture and rheology modifier, and mix the powder materials evenly. Add mixing water and stir evenly. The ratio of mixing water to the total mass of powder materials is 0.08~0.10.

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