A water-resistant and impact-resistant potassium magnesium phosphate repair material and a preparation method thereof

Abstract

The present application provides a water-resistant and impact-resistant potassium magnesium phosphate repair material, which belongs to the technical field of building materials. According to the mass fraction, the material includes: component A: 8-15 parts of acrylamide, 0.1-0.18 parts of initiator, 0.06-0.1 parts of cross-linking agent, 14-24 parts of solvent; component B: 50-90 parts of modified magnesium oxide, 25-30 parts of potassium dihydrogen phosphate, 1-5 parts of retarder, 0.4-1.2 parts of polyvinyl alcohol fiber; the modified magnesium oxide is obtained by treating magnesium oxide with water glass. The present invention not only improves the water resistance of potassium magnesium phosphate cement, but also optimizes the operability during the construction process. The prepared polymer-modified potassium magnesium phosphate repair material has high early strength and impact resistance, and can be widely used in highways, airport runways, military and other projects that require rapid repairs.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and particularly relates to a water-resistant and impact-resistant potassium magnesium phosphate emergency repair material obtained by polymer modification and a preparation method thereof. Background Art

[0002] Ordinary Portland cement is the most widely used building material due to its simple materials, easy access, low cost and convenient construction. At present, the global annual production of Portland cement has reached 4.1 billion tons. Behind this figure is the emission of a large amount of greenhouse gases (carbon dioxide) and huge energy consumption, which have caused serious impacts on the environment. With global warming and the deterioration of the ecological environment, these problems of Portland cement have become more and more prominent. In order to meet these challenges and promote the sustainable development of human society, people have begun to seek a new type of environmentally friendly cementitious material. In this context, magnesium phosphate cement has received widespread attention due to its environmental protection characteristics and excellent performance.

[0003] Potassium magnesium phosphate cement is a new type of inorganic cementitious material, which is produced by the acid-base neutralization reaction of magnesium oxide, soluble phosphate and retarder in a certain proportion, and uses the hydrolysis product of magnesium phosphate as the bonding phase. It has the advantages of early strength, fast hardening, high bonding strength with old concrete, and the ability to maintain strength development at negative temperatures. It has very good application prospects in building emergency repair engineering materials. However, its poor impact resistance, high brittleness and fast setting time seriously restrict its application in rapid repair. If the setting time of potassium magnesium phosphate cement can be extended and its impact resistance and brittleness can be improved, potassium magnesium phosphate cement will be widely used in rapid repair projects such as highways, airport runways, and military.

[0004] The prior art provides some potassium magnesium phosphate repair materials. For example, patent CN113149491A discloses a highly water-resistant potassium magnesium phosphate repair material and a preparation method thereof. The highly water-resistant potassium magnesium phosphate repair material is prepared with magnesium oxide, potassium dihydrogen phosphate, borax and latex powder, and has good water resistance. Patent CN114380521A discloses a slow-setting potassium magnesium phosphate cement and a preparation method thereof. Magnesium oxide is encapsulated in a calcium carbonate capsule wall in the form of microcapsules. During use, the magnesium oxide can be gradually released slowly, thereby solving the problem of short setting time of traditional potassium magnesium phosphate cement. Patent CN 117776587 A discloses an organic-inorganic composite slow-setting toughening agent for magnesium phosphate cement. However, the setting time of this solution is still relatively short.

[0005] However, most of the existing technologies focus on improving the water resistance and setting time of magnesium potassium phosphate cement, with less research on impact resistance and brittleness. At the same time, the improvement process will also have a negative impact on its early strength and durability. Summary of the invention

[0006] In order to solve the above problems, the present application aims to provide a polymer-modified potassium magnesium phosphate emergency repair material, which not only solves the defects of potassium magnesium phosphate cement being water-inresistant and setting too fast, but also improves the impact resistance and has excellent early strength. It can be used for rapid repair projects such as highways, airport runways, and military.

[0007] On the one hand, the present application provides a water-resistant and impact-resistant potassium magnesium phosphate repair material, which comprises, by weight:

[0008] Component A: 8-15 parts of acrylamide, 0.1-0.18 parts of initiator, 0.06-0.1 parts of crosslinking agent, 14-24 parts of solvent;

[0009] Component B: 50-90 parts of modified magnesium oxide, 25-30 parts of potassium dihydrogen phosphate;

[0010] Component C: 1-5 parts of retarder, 0.4-1.2 parts of enhancer;

[0011] In the component B, the modified magnesium oxide is obtained by treating magnesium oxide with water glass.

[0012] In one embodiment, the step of treating the magnesium oxide with water glass comprises: immersing the magnesium oxide in water glass, shaking and soaking it, and then taking it out and drying it.

[0013] In one embodiment, the oscillation method is to place it in a mechanical horizontal oscillator or an electronic horizontal oscillator for oscillation, preferably a mechanical horizontal oscillator, with an oscillation frequency of 60 times / min.

[0014] In one embodiment, the soaking time is not less than 0.5 h, preferably 0.5 to 3 h, and more preferably 1 h.

[0015] In one embodiment, after being taken out, it is placed in an oven at 200-400° C. for drying.

[0016] In one embodiment, the magnesium oxide is dead-burned magnesium oxide obtained by calcining magnesite at 1500° C. to 1800° C.

[0017] Preferably, the dead-burned magnesium oxide is obtained by calcining magnesite at 1700° C., and the MgO content is ≥85%.

[0018] In one embodiment, the water glass is selected from sodium water glass or potassium water glass with a modulus of 3.2 to 3.4.

[0019] Preferably, the water glass is sodium water glass, and the solid content is ≥35%.

[0020] In one embodiment, in the component A, the initiator is selected from one or more of persulfates, sulfites and organic peroxide-ferrous salt systems.

[0021] In one embodiment, the crosslinking agent is selected from one or more of N,N-dimethylformamide, p-phenylenediamine and dimethylaminoethyl methacrylate.

[0022] In one embodiment, the solvent comprises water.

[0023] In one embodiment, the pH value of the acrylamide monomer is >8.0.

[0024] Among them, acrylamide, which is alkaline after dissolution, can polymerize better in the system and quickly form an in-situ polymerization solution.

[0025] In one embodiment, in the component B, the specific surface area of ​​potassium dihydrogen phosphate is ≥ 280 m 2 / kg, thereby enabling potassium dihydrogen phosphate and magnesium ions to have an appropriate reaction rate.

[0026] In one embodiment, the retarder comprises borax.

[0027] In one embodiment, the particle size of the borax is 50-80 mesh.

[0028] In one embodiment, the Young's modulus of the polyvinyl alcohol fiber is ≥380 cN / detx and the length is 6-8 mm.

[0029] On the other hand, the present application provides a method for preparing the water-resistant and impact-resistant potassium magnesium phosphate emergency repair material, the method comprising the following steps:

[0030] Step 1: adding acrylamide, an initiator and a cross-linking agent respectively according to their weight parts into a solvent, stirring and dissolving to obtain an acrylamide in-situ polymerization solution;

[0031] Step 2: Take modified magnesium oxide, potassium dihydrogen phosphate and retarder respectively according to their mass fractions, mix and stir, add the acrylamide in-situ polymerization solution obtained in step 1 and polyvinyl alcohol fiber, stir evenly to obtain the potassium magnesium phosphate emergency repair material.

[0032] In one embodiment, the time interval from the preparation to the use of the emergency repair material is ≤20 minutes.

[0033] In one embodiment, the particle size of the modified magnesium oxide in step 2 is less than 100 mesh, and preferably, the modified magnesium oxide is crushed to 120 mesh.

[0034] On the other hand, the present application provides the use of the emergency repair material in preparing repair products and / or reinforcement products for cement, roads, and buildings.

[0035] Optionally, the roads include but are not limited to urban roads, highways, airport roads, etc.

[0036] This application has at least the following beneficial effects:

[0037] The polymer modified potassium magnesium phosphate repair material prepared in this application has excellent water resistance and impact resistance. Acrylamide can be polymerized in situ under specific initiators and crosslinking agents to form a three-dimensional polymer network, and the hydration product of potassium magnesium phosphate cement is wrapped, and the surface structure of PVA fiber is improved, thereby improving water resistance and impact resistance. 2+ The reaction generates hydrated magnesium silicate gel, which has the function of filling the pores of the repair material, thus making it have good water resistance. At the same time, the magnesium oxide modified by water glass is adhered to the surface of magnesium oxide after drying, forming a natural barrier similar to a protective film, which delays the reaction of magnesium oxide with potassium dihydrogen phosphate. In addition, in order to overcome the polymerization reaction barrier, the acrylamide polymerization system will absorb energy, which will reduce the ambient temperature and slow down the cement hydration. Moreover, the negatively charged acrylic acid ions are adsorbed on the surface of magnesium oxide particles and their hydration products, resulting in electrostatic repulsion and inhibiting the formation of flocculation structure. Even at a low dosage, borax can prolong the setting time and has little effect on the early strength. In addition, since sodium water glass is alkaline, it will increase the alkalinity of the system after dissolving in the aqueous solution, especially sodium water glass with a suitable silicon and alkali metal ratio (modulus) to have better solubility and alkalinity. The pH value of the system increases, which is conducive to the effective polymerization of acrylamide monomer into high relative molecular mass polyacrylamide. At the same time, when the sodium water glass on the surface of magnesium oxide is completely dissolved, under the condition that there are appropriate amounts of initiators and cross-linking agents in the system, the violent acid-base neutralization reaction will release a large amount of heat, which in turn will promote the in-situ polymerization of acrylamide, solving the problem of low early strength of in-situ polymerization in traditional cement. DETAILED DESCRIPTION

[0038] In order to more clearly explain the overall concept of the application, the following is described in detail by way of embodiment. In the following description, a large amount of specific details are provided so as to provide a more thorough understanding of the application. However, it is obvious to those skilled in the art that the application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the application, some technical features well known in the art are not described.

[0039] Unless otherwise specified, the raw materials, reagents, instruments, equipment, etc. involved in the following examples can be obtained through commercial channels, and the use of each instrument and equipment can refer to its conventional operating method.

[0040] In the following examples, the MgO content in the dead-burned magnesium oxide is 85%; the purity of potassium dihydrogen phosphate is 98% and the specific surface area is 280m 2 / kg; the pH value of acrylamide monomer is 8.2; the borax is 70 mesh and the purity is 95%; the Young's modulus of PVA fiber is 380cN / detx and the length is 7mm; the modulus of sodium water glass is 3.2-3.4 and the solid content is ≥35%.

[0041] Example 1

[0042] This embodiment provides a polymer-modified potassium magnesium phosphate repair material, and the raw materials for its preparation include, by weight:

[0043] 50 parts of modified magnesium oxide, 25 parts of potassium dihydrogen phosphate, 8 parts of acrylamide, 0.1 parts of sodium persulfate, 0.06 parts of N,N-dimethylformamide, 1 part of borax, 0.4 parts of PVA fiber, and 14 parts of water.

[0044] Wherein, the modified magnesium oxide is prepared by the following method:

[0045] The dead-burned magnesium oxide was added to sodium water glass (modulus of 3.2, solid content of 35%) and shaken and soaked for 1 hour, then placed in an oven at a temperature of 300°C for 2 hours, cooled to room temperature, and crushed through a 120-mesh sieve to obtain modified magnesium oxide.

[0046] The above raw materials in parts by mass are prepared according to the following method, including:

[0047] Step 1, weighing acrylamide monomer, adding it into water, stirring until completely dissolved, then sequentially adding sodium persulfate and N,N-dimethylformamide, stirring and dissolving to obtain an acrylamide in-situ polymerization solution;

[0048] Step 2: Place modified magnesium oxide, potassium dihydrogen phosphate and borax in a mixer and stir continuously, add acrylamide in-situ polymerization solution and PVA fiber, and stir evenly to obtain polymer-modified potassium magnesium phosphate repair material.

[0049] Example 2

[0050] This embodiment provides a polymer-modified potassium magnesium phosphate repair material, and the raw materials for its preparation include, by weight:

[0051] 90 parts of modified magnesium oxide, 30 parts of potassium dihydrogen phosphate, 15 parts of acrylamide, 0.18 parts of sodium sulfite, 0.1 parts of dimethylaminoethyl methacrylate, 5 parts of borax, 1.2 parts of PVA fiber, and 24 parts of water.

[0052] Wherein, the modified magnesium oxide is prepared by the following method:

[0053] The dead-burned magnesium oxide was added to sodium water glass (modulus of 3.4, solid content of 36%) and shaken and soaked for 1 hour, then placed in an oven at a temperature of 300°C for 2 hours, cooled to room temperature, and crushed through a 120-mesh sieve to obtain modified magnesium oxide.

[0054] The above raw materials in parts by mass are prepared according to the following method, including:

[0055] Step 1, weighing acrylamide monomer, adding it into water, stirring until completely dissolved, then sequentially adding sodium persulfite and dimethylaminoethyl methacrylate, stirring and dissolving to obtain an acrylamide in-situ polymerization solution;

[0056] Step 2: Place modified magnesium oxide, potassium dihydrogen phosphate and borax in a mixer and stir continuously, add acrylamide in-situ polymerization solution and PVA fiber, and stir evenly to obtain polymer-modified potassium magnesium phosphate repair material.

[0057] Example 3

[0058] This embodiment provides a polymer-modified potassium magnesium phosphate repair material, and the raw materials for its preparation include, by weight:

[0059] 80 parts of modified magnesium oxide, 27 parts of potassium dihydrogen phosphate, 12 parts of acrylamide, 0.15 parts of organic peroxide-ferrous salt, 0.08 parts of p-phenylenediamine, 3 parts of borax, 0.8 parts of PVA fiber, and 19 parts of water.

[0060] Wherein, the modified magnesium oxide is prepared by the following method:

[0061] The dead-burned magnesium oxide was added to sodium water glass (modulus of 3.3, solid content of 36%) and shaken and soaked for 1 hour, then placed in an oven at a temperature of 300°C for 2 hours, cooled to room temperature, and crushed through a 120-mesh sieve to obtain modified magnesium oxide.

[0062] The above raw materials in parts by mass are prepared according to the following method, including:

[0063] Step 1, weighing acrylamide monomer, adding it into water, stirring until completely dissolved, and then sequentially adding organic peroxide-ferrous salt and p-phenylenediamine, stirring and dissolving to obtain an acrylamide in-situ polymerization solution;

[0064] Step 2: Place modified magnesium oxide, potassium dihydrogen phosphate and borax in a mixer and stir continuously, add acrylamide in-situ polymerization solution and PVA fiber, and stir evenly to obtain polymer-modified potassium magnesium phosphate repair material.

[0065] Embodiment 4 to Embodiment 9

[0066] The material composition and preparation method of this series of embodiments are substantially the same as those of Embodiment 3, the only difference being that the modulus of sodium water glass and the number of initiators and crosslinking agents are different, as follows:

[0067] Embodiment 4 and Embodiment 5 are the same as Embodiment 3, except that the modulus of sodium water glass is 2.8 and 3.6 respectively;

[0068] Example 6 and Example 7 are the same as Example 3, except that the mass fractions of the initiator are 0.05 parts and 0.3 parts respectively;

[0069] Example 8 and Example 9 are the same as Example 3, except that the weight fractions of the cross-linking agent are 0.01 parts and 0.2 parts respectively.

[0070] Comparative Example 1

[0071] The preparation method of this example is substantially the same as that of Example 3, except that the raw materials and mass fractions of the materials are: 80 parts of modified magnesium oxide, 27 parts of potassium dihydrogen phosphate, 3 parts of borax, 0.8 parts of PVA fiber, and 19 parts of water. That is, no in-situ polymer of acrylamide is used for modification.

[0072] Comparative Example 2

[0073] The material composition and preparation method of this example are substantially the same as those of Example 3, with the only difference being that the modified magnesium oxide treated with sodium water glass is not used, and dead-burned magnesium oxide is directly used.

[0074] Comparative Example 3

[0075] The material composition and preparation method of comparative example 1 of this example are substantially the same, the only difference being that 12 parts of polyacrylamide are added to the raw materials of the material, that is, polyacrylamide is added to the material in the form of an additive.

[0076] The performance of the potassium magnesium phosphate repair materials prepared in the above examples was tested, where:

[0077] The test method of setting time shall refer to GB / T1346-2001 "Test method of water consumption, setting time and stability of cement standard consistency";

[0078] The test methods for compressive strength and tensile bond strength refer to JG / T 336-2011 "Polymer cement mortar for repair of concrete structures";

[0079] The impact resistance test was carried out by the drop hammer method. The size of the test specimen was Φ150 mm, height 35 mm, and age was 28 days. The test specimen was placed on a pad, and a drop tube was placed on the specimen, so that the drop hammer fell freely along the tube. The impact resistance of the specimen was evaluated by the number of times the drop hammer fell when the first visible crack appeared and the number of times the drop hammer fell when the crack was completely cracked.

[0080] The time from preparation to use of each material shall not exceed 20 minutes, starting from the addition of acrylamide in-situ polymerization solution.

[0081] The test results are shown in Table 1.

[0082]

[0083] As can be seen from the results in Table 1, compared with the emergency repair materials without polymer modification (Comparative Example 1), without modified magnesium oxide (Comparative Example 2), and with polyacrylamide added as an additive (Comparative Example 3), the emergency repair materials provided in the embodiments of the present application show obvious advantages in water resistance and impact resistance. For the in-situ polymerized polyacrylamide and sodium water glass modified magnesium oxide in the embodiments, the amount of initiator and crosslinker used to promote the polymerization of acrylamide monomer, and the auxiliary effect of sodium water glass with different moduli on the polymerization of acrylamide monomer after dissolution have an important influence on the structure of the final material. For example, in terms of microstructure, the amount of acrylamide monomer polymerization will be small, and cement cannot be effectively wrapped and the surface structure of the fiber will not be improved. Or, the polymer formed after the in-situ polymerization of acrylamide monomer will have defects such as agglomeration and holes, and then the strength is low, affecting the material performance. Among them, the emergency repair materials prepared in Examples 1 to 3 have a longer setting time, a greater compressive strength in the initial stage, better water resistance, and show excellent impact resistance, which can be used as a preferred embodiment of the present application.

[0084] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A water-resistant and impact-resistant magnesium potassium phosphate repair material, characterized in that: The materials include, by mass: Component A: 8-15 parts of acrylamide, 0.1-0.18 parts of initiator, 0.06-0.1 parts of crosslinking agent, 14-24 parts of solvent; Component B: 50-90 parts of modified magnesium oxide, 25-30 parts of potassium dihydrogen phosphate, 1-5 parts of retarder, 0.4-1.2 parts of polyvinyl alcohol fiber; The retarder is borax; The Young's modulus of the polyvinyl alcohol fiber is ≥380 cN / detx and the length is 6-8 mm; The modified magnesium oxide is obtained by treating magnesium oxide with water glass, and the steps include: immersing the magnesium oxide in water glass, shaking and soaking it, and then taking it out and drying it; The water glass is selected from sodium water glass or potassium water glass with a modulus of 3.2 to 3.4; The preparation method of the emergency repair material comprises the following steps: Step 1: adding acrylamide, an initiator and a cross-linking agent respectively according to their weight parts into a solvent, stirring and dissolving to obtain an acrylamide in-situ polymerization solution; Step 2: Take modified magnesium oxide, potassium dihydrogen phosphate and retarder respectively according to their mass fractions, mix and stir, add the acrylamide in-situ polymerization solution obtained in step 1 and polyvinyl alcohol fiber, stir evenly to obtain the potassium magnesium phosphate emergency repair material.

2. The repair material according to claim 1, characterized in that: The magnesium oxide is dead-burned magnesium oxide obtained by calcining magnesite at 1500° C. to 1800° C.

3. The repair material according to claim 1, characterized in that: In the component A, the initiator is selected from one or more of persulfate, sulfite and organic peroxide-ferrous salt system; and / or, the cross-linking agent is selected from one or more of N,N-dimethylformamide, p-phenylenediamine and dimethylaminoethyl methacrylate; And / or, the solvent is water.

4. The repair material according to claim 1, characterized in that: The pH value of the acrylamide is greater than 8.

0.

5. The repair material according to claim 1, characterized in that: In the component B, the specific surface area of ​​potassium dihydrogen phosphate is ≥ 280m 2 / kg.

6. The repair material according to claim 1, characterized in that: The time interval from the preparation to the use of the emergency repair materials is ≤20 minutes.

7. The repair material according to claim 1, characterized in that: The particle size of the modified magnesium oxide in step 2 is less than 100 mesh.

8. Use of the emergency repair material according to any one of claims 1 to 7 in the preparation of repair products and / or reinforcement products for cement, roads and buildings.

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