A high-strength slow-setting magnesium phosphate cement and its preparation method and application

Abstract

The present invention provides a high-strength retarded magnesium phosphate cement and its preparation method and application, which belongs to the technical field of magnesium phosphate cement. The high-strength retarded magnesium phosphate cement provided by the present invention comprises the following raw materials, calculated by mass: 60 to 95 parts of dead-burned magnesium oxide powder, 20 to 50 parts of phosphate, 3 to 15 parts of composite retarder, 5 to 20 parts of admixture, 8 to 14 parts of fly ash microbeads, 1 to 2 parts of carbon nanotubes, 1 to 5 parts of carbon fiber and 5 to 30 parts of water; the composite retarder comprises sodium tripolyphosphate, zinc acetate, disodium EDTA and polyacrylic acid; the admixture comprises phosphorus slag powder and silica fume. The results of the examples show that the setting time of the high-strength retarded magnesium phosphate cement provided by the present invention is controllable between tens of minutes and more than ten hours, and the 28-day compressive strength of the magnesium phosphate cement is greater than 90 MPa, and it has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium phosphate cement, and in particular to high-strength slow-setting magnesium phosphate cement, a preparation method thereof, and applications thereof. Background Art

[0002] Magnesium phosphate cement is a new type of phosphate repair material that exhibits rapid early strength and hardening, typically composed of magnesium oxide, phosphate, and a retarder. Compared to ordinary Portland cement, magnesium phosphate cement offers advantages such as rapid low-temperature setting, high early strength, reduced shrinkage during drying, and excellent wear and frost resistance. It also exhibits excellent compatibility with existing concrete and biocompatibility. As a result, it is widely used in the rapid repair of roads, bridges, and airport runways, as well as in the solidification of hazardous and radioactive materials, and has important civil and military applications.

[0003] However, magnesium phosphate cement also has some significant drawbacks, such as rapid setting, high hydration heat release, low overall strength, and poor construction operability. In actual projects, due to the sensitivity of magnesium phosphate cement to temperature, even the slightest improper operation will cause the cementitious material to set during mixing, resulting in material failure and engineering accidents. Setting time has become an important factor restricting the application of magnesium phosphate cement, so the performance of magnesium phosphate cement needs to be modified. However, the gelling principle of magnesium phosphate cement and ordinary Portland cement is different, which is to produce components such as hydrated calcium silicate through hydration reaction. The reaction mechanism of magnesium phosphate cement is acid-base reaction, forming chemically bonded compounds to produce gelling effect. Its main strength-providing components are compounds such as magnesium potassium phosphate. This makes many reinforcement methods that can be used in Portland cement become inapplicable to magnesium phosphate cement.

[0004] Extensive research into the basic components, modified materials, and setting retarders of magnesium phosphate cement has revealed that the type and dosage of the retarder have the most significant impact on the setting time of magnesium phosphate cementitious materials. However, current retarders can only slow the setting rate of magnesium phosphate cement, preventing severe strength loss, but are unable to regulate its setting time. This significantly limits its application scenarios, and the resulting magnesium phosphate cement has mediocre mechanical properties, hindering its further promotion and application.

[0005] Therefore, how to achieve controllable regulation of the setting time of magnesium phosphate cement and improve the mechanical properties of magnesium phosphate cement has become a technical problem to be solved urgently in this field. Summary of the Invention

[0006] The object of the present invention is to provide a high-strength retarded magnesium phosphate cement and a preparation method and application thereof. The high-strength retarded magnesium phosphate cement provided by the present invention can realize controllable adjustment of the setting time, and the magnesium phosphate cement has excellent mechanical properties.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a high-strength retarded magnesium phosphate cement, which comprises the following raw materials, calculated by weight: 60-95 parts of dead-burned magnesium oxide powder, 20-50 parts of phosphate, 3-15 parts of composite retarder, 5-20 parts of admixture, 8-14 parts of fly ash microbeads, 1-2 parts of carbon nanotubes, 1-5 parts of carbon fibers, and 5-30 parts of water;

[0009] The composite retarder comprises sodium tripolyphosphate, zinc acetate, disodium EDTA and polyacrylic acid; and the admixture comprises phosphorus slag powder and silica fume.

[0010] Preferably, the average particle size of the dead-burned magnesia powder is 30-40 μm, and the content of magnesia in the dead-burned magnesia powder is ≥92%.

[0011] Preferably, the phosphate includes one or two of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, aniline hypophosphite and isopropanolamine phosphate.

[0012] Preferably, the composite retarder comprises, by mass percentage, 27-43% sodium tripolyphosphate, 12-25% zinc acetate, 17-22% disodium EDTA and the balance polyacrylic acid.

[0013] Preferably, the composite retarder comprises, by mass percentage, 30-35% of sodium tripolyphosphate, 15-20% of zinc acetate, 18-21% of disodium EDTA and the balance of polyacrylic acid.

[0014] Preferably, the mass ratio of the phosphorus slag powder to silica fume is 1:(0.1-2).

[0015] Preferably, the average particle size of the fly ash microbeads is ≤0.5 μm, and the specific surface area of ​​the fly ash microbeads is ≥1000 m 2 / kg.

[0016] Preferably, the parameters of the carbon fiber include: length of 2 to 10 mm, diameter of 10 to 50 μm, tensile strength of 1500 to 2400 MPa, and elongation at break of 8 to 12%.

[0017] The present invention provides a method for preparing the high-strength retarded magnesium phosphate cement described in the above technical solution, comprising the following steps:

[0018] (1) mixing dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes and carbon fibers to obtain a mixture;

[0019] (2) mixing the composite retarder and water, adding the mixture to the mixture obtained in step (1) and stirring the mixture, and finally curing the mixture to obtain high-strength retarded magnesium phosphate cement.

[0020] The present invention provides the use of the high-strength retarded magnesium phosphate cement described in the above technical solution or the high-strength retarded magnesium phosphate cement prepared by the preparation method described in the above technical solution in rapid repair and solidification of harmful and radioactive substances.

[0021] The present invention provides a high-strength slow-setting magnesium phosphate cement, which comprises the following raw materials in parts by mass: 60-95 parts of dead-burned magnesium oxide powder, 20-50 parts of phosphate, 3-15 parts of composite retarder, 5-20 parts of admixture, 8-14 parts of fly ash microbeads, 1-2 parts of carbon nanotubes, 1-5 parts of carbon fiber and 5-30 parts of water; the composite retarder comprises sodium tripolyphosphate, zinc acetate, disodium EDTA and polyacrylic acid; the admixture comprises phosphorus slag powder and silica fume. In the present invention, dead-burned magnesium oxide powder can provide a large amount of magnesium oxide, which provides an acidic environment and acid radical ions through phosphate, and undergoes a hydration reaction to generate a hydration product that improves the strength of magnesium phosphate cement, thereby obtaining high-performance magnesium phosphate cement; by using the composite retarder, the magnesium oxide can react with the Mg in the magnesium phosphate cement paste to form a hydration product that improves the strength of the magnesium phosphate cement. 2+It has a strong chelating ability, reduces the concentration of magnesium ions, and thus delays the formation of hydration products. Compared with the same amount of a single type of retarder, the four components in the composite retarder can play a good synergistic role, further improving its retarding effect; by controlling the dosage of the composite retarder, the setting time of magnesium phosphate cement can be controlled, making it controllable between tens of minutes and more than ten hours, so that it can be adjusted accordingly according to actual working conditions, greatly expanding the application scenarios of magnesium phosphate cement; by adding admixtures, on the one hand, the hydration reaction inside the magnesium phosphate cement can be inhibited in the early stage, thereby reducing the hydration rate, and on the other hand, the degree of hydration in the later stage can be increased, thereby improving the strength and water resistance of magnesium phosphate cement; fly ash The active ingredient in the microbead can react chemically with the alkaline substance in magnesium phosphate cement, promote the hydration reaction of cement, improve the strength and durability of magnesium phosphate cement, and on the other hand can be filled in the gaps between magnesium phosphate cement particles, reduce the porosity of magnesium phosphate cement, thereby further improving the density and strength of magnesium phosphate cement; carbon nanotubes can significantly improve the internal structure of magnesium phosphate cement, improve its compactness, and then improve the mechanical properties and durability of magnesium phosphate cement; utilize the bridging polymerization effect produced by carbon fiber in cement-based materials to improve the tensile and flexural strength and deformation capacity of magnesium phosphate cement, while achieving the effect of consuming load energy, thereby significantly enhancing the toughness and crack resistance of magnesium phosphate cement-based materials. The present invention, by optimizing the composition and dosage of phosphate cement, can not only improve the early strength of phosphate cement, but also significantly improve the retarding effect, increase the setting time of phosphate cement, and improve the controllability of phosphate cement. The results of the examples show that the setting time of the high-strength retarded magnesium phosphate cement provided by the present invention can be controlled between tens of minutes and more than ten hours. At the same time, the compressive strength of the magnesium phosphate cement at 28 days is greater than 90 MPa, and it has excellent mechanical properties. DETAILED DESCRIPTION

[0022] The present invention provides a high-strength retarded magnesium phosphate cement, which comprises the following raw materials, calculated by weight: 60-95 parts of dead-burned magnesium oxide powder, 20-50 parts of phosphate, 3-15 parts of composite retarder, 5-20 parts of admixture, 8-14 parts of fly ash microbeads, 1-2 parts of carbon nanotubes, 1-5 parts of carbon fibers and 5-30 parts of water.

[0023] The high-strength slow-setting magnesium phosphate cement provided by the present invention includes 60 to 95 parts by mass of dead-burned magnesium oxide powder. In the present invention, the average particle size of the dead-burned magnesium oxide powder is preferably 30 to 40 μm; the magnesium oxide content in the dead-burned magnesium oxide powder is preferably ≥ 92%. The present invention uses dead-burned magnesium oxide powder as the main raw material of magnesium phosphate cement, which is not only widely available but also has a high magnesium oxide content, ensuring that the prepared magnesium phosphate cement has excellent mechanical properties. As an embodiment of the present invention, the mass fraction of the dead-burned magnesium oxide powder can be 65, 70, 75, 80, 85, or 90 parts; the average particle size of the dead-burned magnesium oxide powder can be 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, or 40 μm.

[0024] Based on the mass fraction of dead-burned magnesium oxide powder being 60 to 95 parts, the high-strength slow-setting magnesium phosphate cement provided by the present invention includes 20 to 50 parts of phosphate. In the present invention, the phosphate preferably includes one or two of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, aniline hypophosphite and isopropanolamine phosphate. The present invention provides an acidic environment and acid radical ions for the hydration reaction by adding phosphate as a matrix component of the magnesium phosphate cement, thereby reacting with the dead-burned magnesium oxide powder to generate a hydration product that improves the strength of the magnesium phosphate cement, thereby obtaining high-performance magnesium phosphate cement. As an embodiment of the present invention, the mass fraction of the phosphate can be 25 parts, 30 parts, 35 parts, 40 parts or 45 parts.

[0025] Based on the mass fraction of dead-burned magnesium oxide powder of 60 to 95 parts, the high-strength slow-setting magnesium phosphate cement provided by the present invention includes 3 to 15 parts of composite retarder. In the present invention, the composite retarder includes sodium tripolyphosphate, zinc acetate, disodium EDTA and polyacrylic acid. In the present invention, the composite retarder preferably includes sodium tripolyphosphate 27 to 43%, zinc acetate 12 to 25%, disodium EDTA 17 to 22% and the balance polyacrylic acid, and more preferably includes sodium tripolyphosphate 30 to 35%, zinc acetate 15 to 20%, disodium EDTA 18 to 21% and the balance polyacrylic acid. The present invention uses the above-mentioned components as a composite retarder, which can be combined with Mg in magnesium phosphate cement paste. 2+It has a strong complexing ability, reduces the concentration of magnesium ions, and thus delays the generation of hydration products; at the same time, by the composite use of the above four components, relative to the same amount of a single type of retarder, it can play a good synergistic role and further improve its retarding effect; by controlling the amount of the composite retarder, the setting time of magnesium phosphate cement can be controlled to be controllable between tens of minutes and more than ten hours, so that it can be adjusted accordingly according to the actual working conditions, greatly expanding the application scenarios of magnesium phosphate cement. As an embodiment of the present invention, the mass fraction of the composite retarder can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts or 14 parts.

[0026] The high-strength slow-setting magnesium phosphate cement provided by the present invention includes 5 to 20 parts of admixtures, based on 60 to 95 parts by mass of dead-burned magnesium oxide powder. In the present invention, the admixtures include phosphorus slag powder and silica fume; the mass ratio of the phosphorus slag powder to silica fume is preferably 1: (0.1 to 2). In the present invention, the content of P2O5 in the phosphorus slag powder is preferably ≥3wt%, and the content of soluble fluoride is preferably ≥2wt%; the specific surface area of ​​the phosphorus slag powder is preferably 300 to 600m 2 / kg; the average particle size of the silica fume is preferably 0.1 to 0.3 μm. The present invention adopts phosphorus slag powder and silica fume as admixtures. The phosphorus slag powder can inhibit the hydration reaction inside the magnesium phosphate cement in the early stage, thereby reducing the hydration rate. At the same time, the phosphorus content is high and the specific surface area is large, which can react with magnesium oxide to reduce the content of free magnesium oxide in the cement in the later stage, improve the degree of hydration, and thus improve the strength and water resistance of magnesium phosphate cement; while silica fume can reduce the early hydration rate of magnesium phosphate cement and increase its early strength, which is beneficial to the normal construction and application of magnesium phosphate cement. As an embodiment of the present invention, the mass fraction of the admixture can be 8 parts, 10 parts, 12 parts, 15 parts or 18 parts; the specific surface area of ​​the phosphorus slag powder can be 400 to 500m 2 / kg; the average particle size of the silica fume may be 0.15 to 0.25 μm.

[0027] The high-strength slow-setting magnesium phosphate cement provided by the present invention includes 8 to 14 parts of fly ash microspheres, based on 60 to 95 parts by mass of dead-burned magnesium oxide powder. In the present invention, the average particle size of the fly ash microspheres is preferably ≤0.5 μm; the specific surface area of ​​the fly ash microspheres is preferably ≥1000 m 2 / kg. The present invention adds fly ash microbeads to magnesium phosphate cement. On the one hand, the active ingredients in the fly ash can chemically react with the alkaline substances in the magnesium phosphate cement to promote the hydration reaction of the cement and improve the strength and durability of the magnesium phosphate cement. On the other hand, the addition in the form of fly ash microbeads can fill the gaps between the magnesium phosphate cement particles, reducing the porosity of the magnesium phosphate cement, thereby further improving the density and strength of the magnesium phosphate cement. As an embodiment of the present invention, the mass fraction of the fly ash microbeads can be 65 parts, 70 parts, 75 parts, 80 parts, 85 parts or 90 parts; the average particle size of the fly ash microbeads can be 0.01 to 0.5 μm; the specific surface area of ​​the fly ash microbeads can be 1200 to 1500 m 2 / kg.

[0028] The high-strength, retarded magnesium phosphate cement provided by the present invention includes 1-2 parts of carbon nanotubes, based on 60-95 parts by weight of dead-burned magnesium oxide powder. By adding a certain amount of carbon nanotubes to the magnesium phosphate cement, the present invention can significantly improve the internal structure of the magnesium phosphate cement, enhance its compactness, and thereby improve the mechanical properties and durability of the magnesium phosphate cement. As one embodiment of the present invention, the carbon nanotubes can be present in an amount of 1.2 parts, 1.4 parts, 1.6 parts, or 1.8 parts by weight.

[0029] The high-strength slow-setting magnesium phosphate cement provided by the present invention includes 1 to 5 parts of carbon fiber, based on 60 to 95 parts by mass of dead-burned magnesium oxide powder. In the present invention, the parameters of the carbon fiber preferably include: a length of 2 to 10 mm, a diameter of 10 to 50 μm, a tensile strength of 1500 to 2400 MPa, and an elongation at break of 8 to 12%. The present invention selects carbon fibers with excellent tensile strength and tensile properties as raw materials and adds them to the magnesium phosphate cement. The bridging polymerization effect of the carbon fibers in the cement-based material is utilized to improve the tensile and flexural strength and deformation capacity of the magnesium phosphate cement, while also achieving the effect of dissipating load energy, thereby significantly enhancing the toughness and crack resistance of the magnesium phosphate cement-based material. As an embodiment of the present invention, the mass fraction of the carbon fiber can be 2, 3, or 4 parts; the parameters of the carbon fiber can be: a length of 4 to 8 mm, a diameter of 20 to 30 μm, a tensile strength of 1800 to 2300 MPa, and an elongation at break of 8 to 12%.

[0030] The high-strength, retarded magnesium phosphate cement provided by the present invention includes 5 to 30 parts of water, based on 60 to 95 parts by weight of dead-burned magnesium oxide powder. By controlling the amount of water, the present invention can, on the one hand, impart better fluidity to the slurry, and on the other hand, ensure the hydration reaction of the magnesium phosphate cement. As one embodiment of the present invention, the water content can be 10 parts, 15 parts, 20 parts, or 25 parts by weight.

[0031] The high-strength, retarded magnesium phosphate cement provided by the present invention preferably also includes 40 to 80 parts of aggregate, based on 60 to 95 parts by mass of dead-burned magnesium oxide powder. In the present invention, the aggregate is preferably fine sand; the aggregate particle size is preferably 0.08 to 2.5 mm; the SiO2 content in the fine sand is preferably ≥ 96%; and the mud content is preferably < 0.2%. By adding fine sand as aggregate, the strength of the high-strength, retarded magnesium phosphate cement can be further improved.

[0032] In the present invention, unless otherwise specified, the above raw materials are all commercially available products well known to those skilled in the art or are prepared using preparation methods well known to those skilled in the art.

[0033] In the present invention, dead-burned magnesium oxide powder can provide a large amount of magnesium oxide, which provides an acidic environment and acid radical ions through phosphate, and the hydration reaction generates a hydration product that improves the strength of magnesium phosphate cement, thereby obtaining high-performance magnesium phosphate cement; by using a composite retarder, it can react with the Mg in the magnesium phosphate cement paste. 2+ It has a strong chelating ability, reduces the concentration of magnesium ions, and thus delays the formation of hydration products. Compared with the same amount of a single type of retarder, the four components in the composite retarder can play a good synergistic role, further improving its retarding effect; by controlling the dosage of the composite retarder, the setting time of magnesium phosphate cement can be controlled, making it controllable between tens of minutes and more than ten hours, so that it can be adjusted accordingly according to actual working conditions, greatly expanding the application scenarios of magnesium phosphate cement; by adding admixtures, on the one hand, the hydration reaction inside the magnesium phosphate cement can be inhibited in the early stage, thereby reducing the hydration rate, and on the other hand, the degree of hydration in the later stage can be increased, thereby improving the strength and water resistance of magnesium phosphate cement; fly ash The active ingredient in the microbead can react chemically with the alkaline substance in magnesium phosphate cement, promote the hydration reaction of cement, improve the strength and durability of magnesium phosphate cement, and on the other hand can be filled in the gaps between magnesium phosphate cement particles, reduce the porosity of magnesium phosphate cement, thereby further improving the density and strength of magnesium phosphate cement; carbon nanotubes can significantly improve the internal structure of magnesium phosphate cement, improve its compactness, and then improve the mechanical properties and durability of magnesium phosphate cement; utilize the bridging polymerization effect produced by carbon fiber in cement-based materials to improve the tensile and flexural strength and deformation capacity of magnesium phosphate cement, while achieving the effect of consuming load energy, thereby significantly enhancing the toughness and crack resistance of magnesium phosphate cement-based materials. The present invention, by optimizing the composition and dosage of phosphate cement, can not only improve the early strength of phosphate cement, but also significantly improve the retarding effect, increase the setting time of phosphate cement, and improve the controllability of phosphate cement.

[0034] The present invention also provides a method for preparing the high-strength retarded magnesium phosphate cement described in the above technical solution, comprising the following steps:

[0035] (1) mixing dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes and carbon fibers to obtain a mixture;

[0036] (2) mixing the composite retarder and water, adding the mixture to the mixture obtained in step (1) and stirring the mixture, and finally curing the mixture to obtain high-strength retarded magnesium phosphate cement.

[0037] The invention mixes dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes and carbon fibers to obtain a mixture.

[0038] In the present invention, the mixing of the dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes, and carbon fibers is preferably performed in a cement mortar mixer. The present invention does not particularly limit the specific model or source of the cement mortar mixer; any commercially available cement mortar mixer familiar to those skilled in the art can be used. In an embodiment of the present invention, the cement mortar mixer is a JJ-15 model.

[0039] In the present invention, the dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes, and carbon fibers are preferably mixed by first mixing the dead-burned magnesium oxide powder, phosphate, admixture, and fly ash microbeads, and then adding the carbon nanotubes and carbon fibers in 2 to 5 portions to form a mixture. In the present invention, the mixing is preferably performed under stirring conditions. The present invention does not specifically limit the stirring rate; it can be determined based on the technical common sense of those skilled in the art to ensure uniform mixing of the components. In the present invention, adding the carbon nanotubes and carbon fibers in 2 to 5 portions facilitates their uniform dispersion in the mixture.

[0040] In the present invention, when the raw materials of the high-strength retarded magnesium phosphate cement further include aggregate, the aggregate is preferably mixed with dead-burned magnesium oxide powder, phosphate, admixtures and fly ash microbeads.

[0041] After obtaining the mixture, the present invention mixes the composite retarder with water, then adds the composite retarder into the mixture for stirring, and finally performs curing to obtain high-strength retarded magnesium phosphate cement.

[0042] In the present invention, the stirring time is preferably 40 to 240 seconds. The present invention does not specifically limit the stirring rate; it can be determined based on the technical common sense of those skilled in the art, as long as the composite retarder and the components are uniformly mixed. As one embodiment of the present invention, the stirring time can be 60 seconds, 80 seconds, 100 seconds, 120 seconds, 140 seconds, 160 seconds, 180 seconds, 200 seconds, or 220 seconds.

[0043] After stirring, the present invention preferably pours the stirred slurry into a mold and then cures it. The present invention does not specifically limit the material and size of the mold, and molds familiar to those skilled in the art can be used. The present invention does not specifically limit the specific operation of pouring the slurry into the mold, and operations familiar to those skilled in the art can be used.

[0044] The present invention does not specifically limit the specific curing method; curing can be performed using any method known to those skilled in the art. In embodiments of the present invention, the curing temperature can be room temperature, and the curing method is natural curing. During the natural curing process, the magnesium phosphate cement is kept moist by watering, allowing the magnesium phosphate cement to gradually harden. In the present invention, the mold is preferably removed after curing for 2 to 5 hours.

[0045] The preparation method provided by the present invention is simple and can be prepared using existing equipment. In addition, during the preparation process, the magnesium phosphate cement will not coagulate too quickly or release a large amount of heat during hydration, which would otherwise cause poor construction operability. This method is conducive to the large-scale promotion and use of phosphate cement.

[0046] The present invention also provides the use of the high-strength retarded magnesium phosphate cement described in the above technical solution or the high-strength retarded magnesium phosphate cement prepared by the preparation method described in the above technical solution in rapid repair and solidification of harmful and radioactive substances.

[0047] In the present invention, the rapid repair preferably includes rapid repair of roads, bridges and airports.

[0048] The present invention has no special limitation on the specific operation of the application, and conventional application operations well known to those skilled in the art may be used.

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0050] Example 1

[0051] A high-strength retarded magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0052] The average particle size of the dead-burned magnesium oxide powder is 34.5 μm, and the magnesium oxide content in the dead-burned magnesium oxide powder is 93.6%; the phosphate is potassium dihydrogen phosphate; the composite retarder is 37% sodium tripolyphosphate, 23% zinc acetate, 18% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:2, the content of P2O5 in the phosphorus slag powder is 3.7wt%, the content of soluble fluoride is 2.1wt%, and the specific surface area of ​​the phosphorus slag powder is 543m 2 / kg; the average particle size of the silica fume is 0.24μm; the average particle size of the fly ash microbeads is 0.43μm, and the specific surface area of ​​the fly ash microbeads is 1246m 2 / kg; the carbon fiber has a length of 2 to 10 mm, a diameter of 10 to 50 μm, a tensile strength of 1500 to 2400 MPa, and an elongation at break of 8 to 12%;

[0053] The preparation method of the high-strength retarded magnesium phosphate cement is:

[0054] (1) First, dead-burned magnesium oxide powder, phosphate, admixture and fly ash microbeads were added to a JJ-15 cement mortar mixer and stirred for 60 seconds. Then, carbon nanotubes and carbon fibers were added three times with an interval of 30 seconds between each addition. Finally, the mixture was stirred for 60 seconds to obtain a mixture.

[0055] (2) The composite retarder and water are mixed evenly, and then added to the mixture obtained in step (1) and stirred for 120 seconds. The stirred slurry is then poured into a mold, and finally demolded after curing in air for 3 hours, and then continued to be naturally cured to obtain high-strength retarded magnesium phosphate cement.

[0056] Example 2

[0057] A high-strength retarded magnesium phosphate cement, comprising, by weight, 75 parts of dead-burned magnesium oxide powder, 28 parts of phosphate, 12 parts of a composite retarder, 14 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0058] The phosphate is ammonium dihydrogen phosphate; the composite retarder is 35% sodium tripolyphosphate, 25% zinc acetate, 17% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:1.5;

[0059] Other conditions are the same as in Example 1.

[0060] Example 3

[0061] A high-strength retarded magnesium phosphate cement, comprising, by weight, 68 parts of dead-burned magnesium oxide powder, 34 parts of phosphate, 9 parts of a composite retarder, 16 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0062] In terms of mass percentage, the composite retarder is composed of 35% sodium tripolyphosphate, 25% zinc acetate, 17% disodium EDTA and the balance polyacrylic acid; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:1.5;

[0063] Other conditions are the same as in Example 1.

[0064] Example 4

[0065] A high-strength retarded magnesium phosphate cement, comprising, by weight, 72 parts of dead-burned magnesium oxide powder, 30 parts of phosphate, 6 parts of a composite retarder, 16 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0066] The composite retarder is composed of 41% sodium tripolyphosphate, 18% zinc acetate, 20% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:1.8;

[0067] Other conditions are the same as in Example 1.

[0068] Example 5

[0069] A high-strength retarded magnesium phosphate cement, comprising, by weight, 65 parts of dead-burned magnesium oxide powder, 27 parts of phosphate, 3 parts of a composite retarder, 11 parts of an admixture, 12 parts of fly ash microbeads, 2 parts of carbon nanotubes, 3 parts of carbon fibers, and 15 parts of water;

[0070] The composite retarder is composed of 41% sodium tripolyphosphate, 18% zinc acetate, 20% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:0.9;

[0071] Other conditions are the same as in Example 1.

[0072] Example 6

[0073] A high-strength retarded magnesium phosphate cement, comprising, by weight, 65 parts of dead-burned magnesium oxide powder, 27 parts of phosphate, 3 parts of a composite retarder, 8 parts of an admixture, 12 parts of fly ash microbeads, 2 parts of carbon nanotubes, 3 parts of carbon fibers, and 15 parts of water;

[0074] The composite retarder is composed of 41% sodium tripolyphosphate, 18% zinc acetate, 20% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:0.9;

[0075] Other conditions are the same as in Example 1.

[0076] Example 7

[0077] A high-strength retarded magnesium phosphate cement, comprising, by weight, 72 parts of dead-burned magnesium oxide powder, 30 parts of phosphate, 6 parts of a composite retarder, 5 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0078] Other conditions are the same as those in Example 4.

[0079] Example 8

[0080] A high-strength retarded magnesium phosphate cement, comprising, by weight, 72 parts of dead-burned magnesium oxide powder, 30 parts of phosphate, 6 parts of a composite retarder, 8 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0081] Other conditions are the same as those in Example 4.

[0082] Example 9

[0083] A high-strength retarded magnesium phosphate cement, comprising, by weight, 72 parts of dead-burned magnesium oxide powder, 30 parts of phosphate, 6 parts of a composite retarder, 12 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0084] Other conditions are the same as those in Example 4.

[0085] Example 10

[0086] A high-strength retarded magnesium phosphate cement, comprising, by weight, 72 parts of dead-burned magnesium oxide powder, 30 parts of phosphate, 6 parts of a composite retarder, 20 parts of an admixture, 9 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 15 parts of water;

[0087] Other conditions are the same as those in Example 4.

[0088] Example 11

[0089] A high-strength retarded magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, 16 parts of water, and 63 parts of aggregate.

[0090] The average particle size of the dead-burned magnesium oxide powder is 34.5 μm, and the magnesium oxide content in the dead-burned magnesium oxide powder is 93.6%; the phosphate is potassium dihydrogen phosphate; the composite retarder is 37% sodium tripolyphosphate, 23% zinc acetate, 18% disodium EDTA and the balance polyacrylic acid in terms of mass percentage; the admixture is composed of phosphorus slag powder and silica fume in a mass ratio of 1:2, the content of P2O5 in the phosphorus slag powder is 3.7wt%, the content of soluble fluoride is 2.1wt%, and the specific surface area of ​​the phosphorus slag powder is 543m 2 / kg; the average particle size of the silica fume is 0.24μm; the average particle size of the fly ash microbeads is 0.43μm, and the specific surface area of ​​the fly ash microbeads is 1246m 2 / kg; the carbon fiber has a length of 2 to 10 mm, a diameter of 10 to 50 μm, a tensile strength of 1500 to 2400 MPa, and an elongation at break of 8 to 12%; the aggregate is fine sand with a particle size of 0.08 to 2.5 mm, the SiO2 content in the fine sand is ≥96%, and the mud content of the fine sand is <0.2%;

[0091] The preparation method of the high-strength retarded magnesium phosphate cement is:

[0092] (1) First, dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads and aggregate were added to a JJ-15 cement mortar mixer and stirred for 60 seconds. Then, carbon nanotubes and carbon fibers were added three times with an interval of 30 seconds each time. Finally, the mixture was stirred for 60 seconds to obtain a mixture.

[0093] (2) The composite retarder and water are mixed evenly, and then added to the mixture obtained in step (1) and stirred for 120 seconds. The stirred slurry is then poured into a mold, and finally demolded after curing in air for 3 hours, and then continued to be naturally cured to obtain high-strength retarded magnesium phosphate cement.

[0094] Comparative Example 1

[0095] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 18 parts of admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0096] Other conditions are the same as in Example 1.

[0097] Comparative Example 2

[0098] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 1 part of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0099] Other conditions are the same as in Example 1.

[0100] Comparative Example 3

[0101] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 2 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0102] Other conditions are the same as in Example 1.

[0103] Comparative Example 4

[0104] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0105] Calculated by mass percentage, the composite retarder is 50% sodium tripolyphosphate and 50% zinc acetate;

[0106] Other conditions are the same as in Example 1.

[0107] Comparative Example 5

[0108] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of sodium tripolyphosphate, 18 parts of admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0109] Other conditions are the same as in Example 1.

[0110] Comparative Example 6

[0111] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0112] Calculated by mass percentage, the composite retarder is 50% disodium EDTA and 50% polyacrylic acid;

[0113] Other conditions are the same as in Example 1.

[0114] Comparative Example 7

[0115] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of disodium EDTA, 18 parts of admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0116] Other conditions are the same as in Example 1.

[0117] Comparative Example 8

[0118] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0119] Other conditions are the same as in Example 1.

[0120] Comparative Example 9

[0121] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of silica fume, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, 2 parts of carbon fibers, and 16 parts of water;

[0122] Other conditions are the same as in Example 1.

[0123] Comparative Example 10

[0124] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon fiber, and 16 parts of water;

[0125] Other conditions are the same as in Example 1.

[0126] Comparative Example 11

[0127] A magnesium phosphate cement, comprising, by weight, 70 parts of dead-burned magnesium oxide powder, 32 parts of phosphate, 15 parts of a composite retarder, 18 parts of an admixture, 10 parts of fly ash microbeads, 2 parts of carbon nanotubes, and 16 parts of water;

[0128] Other conditions are the same as in Example 1.

[0129] The setting time of the magnesium phosphate cement provided in Examples 1 to 10 and Comparative Examples 1 to 11 was measured according to the test method of "Setting Time" in GB / T1346-2011 "Test Method for Standard Consistency, Setting Time and Soundness of Cement"; the compressive strength of the magnesium phosphate cement provided in Examples 1 to 10 and Comparative Examples 1 to 11 was tested at 1 day, 3 days and 28 days according to "Determination of Compressive Strength" in T / CMMA10-2023 "Magnesium Phosphate Composite Materials". The results are shown in Table 1:

[0130] Table 1 Setting time and compressive strength of magnesium phosphate cement provided by Examples 1 to 10 and Comparative Examples 1 to 11

[0131]

[0132]

[0133] Table 1 is analyzed: It can be seen from the changes in the setting time in Examples 1 to 5 and Comparative Examples 1 to 3 that with the increase in the amount of the composite retarder in the high-strength retarded magnesium phosphate cement, the setting time of the high-strength retarded magnesium phosphate cement shows a significant improvement trend. When the amount of the composite retarder varies within 3 to 15 parts, the setting time of the high-strength retarded magnesium phosphate cement varies within a period of tens of minutes to several hours, indicating that the composite retarder provided by the present invention can have a good retarding effect, and by controlling the amount of the composite retarder, the setting time of the high-strength retarded magnesium phosphate cement can be controlled, thereby making the high-strength retarded magnesium phosphate cement suitable for different application scenarios; from the comparison of Examples 5 to 10, it can be seen that when the amount of the composite retarder is the same, with the increase in the amount of the admixture, the setting time of the magnesium phosphate cement also shows a slight increase trend, indicating that the admixture can also play a certain retarding effect and can also improve the mechanical properties of the magnesium phosphate cement; from Examples 1 and 11, it can be seen that without adding aggregate , the prepared magnesium phosphate cement has very high compressive strength, and after adding aggregate, its compressive strength can be further improved, thereby obtaining an ultra-high performance magnesium phosphate cement composite material; by comparing Example 1 with Comparative Examples 4 to 7, it can be seen that when the amount of retarder is the same, the composite retarder formed by using a single type of retarder or two retarders is significantly worse than the composite retarder provided by the present invention, indicating that the composite retarder provided by the present invention has a better retarding effect; by comparing Example 1 with Comparative Example 8, it can be seen that when the addition of admixtures is omitted, the setting time and mechanical properties of magnesium phosphate cement are significantly reduced, indicating that admixtures can improve the retarding effect and the mechanical properties of magnesium phosphate cement; by comparing Example 1 with Comparative Examples 9 to 10, it can be seen that when carbon fibers or carbon nanotubes are omitted, the setting time of magnesium phosphate cement does not change significantly, while the mechanical properties of magnesium phosphate cement are significantly reduced, indicating that carbon fibers and carbon nanotubes can improve the mechanical properties of magnesium phosphate cement.

[0134] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A high-strength retarded magnesium phosphate cement comprising the following raw materials, calculated by weight: 60-95 parts of dead-burned magnesium oxide powder, 20-50 parts of phosphate, 3-15 parts of composite retarder, 5-20 parts of admixture, 8-14 parts of fly ash microspheres, 1-2 parts of carbon nanotubes, 1-5 parts of carbon fiber, and 5-30 parts of water; Calculated by mass percentage, the composite retarder comprises 27-43% sodium tripolyphosphate, 12-25% zinc acetate, 17-22% disodium EDTA and the balance polyacrylic acid; the admixture comprises phosphorus slag powder and silica fume.

2. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that The average particle size of the dead-burned magnesium oxide powder is 30-40 μm, and the content of magnesium oxide in the dead-burned magnesium oxide powder is ≥92%.

3. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that The phosphate includes one or two of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, aniline hypophosphite and isopropanolamine phosphate.

4. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that Calculated by mass percentage, the composite retarder comprises 30-35% of sodium tripolyphosphate, 15-20% of zinc acetate, 18-21% of disodium EDTA and the balance of polyacrylic acid.

5. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that The mass ratio of the phosphorus slag powder to the silica fume is 1:(0.1~2).

6. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that The average particle size of the fly ash microbeads is ≤0.5 μm, and the specific surface area of ​​the fly ash microbeads is ≥1000 m 2 / kg.

7. The high-strength slow-setting magnesium phosphate cement according to claim 1, characterized in that: The parameters of the carbon fiber include: length of 2-10 mm, diameter of 10-50 μm, tensile strength of 1500-2400 MPa, and elongation at break of 8-12%.

8. The method for preparing the high-strength slow-setting magnesium phosphate cement according to any one of claims 1 to 7, comprising the following steps: (1) mixing dead-burned magnesium oxide powder, phosphate, admixture, fly ash microbeads, carbon nanotubes and carbon fibers to obtain a mixture; (2) The composite retarder and water are mixed, and then added to the mixture obtained in step (1) for stirring, and finally cured to obtain high-strength retarded magnesium phosphate cement.

9. Use of the high-strength retarded magnesium phosphate cement according to any one of claims 1 to 7 or the high-strength retarded magnesium phosphate cement prepared by the preparation method according to claim 8 in rapid repair and solidification of harmful and radioactive materials.

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