A magnesium phosphate bead for emergency repair cement capable of melting ice and removing snow, a preparation method thereof, and a repair method

Abstract

The present application relates to a kind of magnesium phosphate beads for emergency repair cement that can melt ice and remove snow, its preparation method and repair method, the beads include PVA water-soluble film and content, content includes by mass fraction: dead-burned magnesia 2-3 parts, ammonium dihydrogen phosphate 1 part, retarder 0.15-0.25 parts, acrylamide 0.3-0.6 parts, ammonium persulfate initiator 0.03-0.06 parts, fine aggregate 3.98-4.41 parts. After stirring and mixing each component, the mixed material is obtained, and the beads are prepared by wrapping with PVA water-soluble film according to different mass fractions. The present application determines the total amount of magnesium phosphate cement concrete required for the repair area and the mass of magnesium phosphate beads and water, places the required magnesium phosphate beads in the position to be repaired, adds water, and the components in the film react to complete the repair. The present application only needs to place a certain amount of magnesium phosphate beads and water at the repair position to achieve repair, simplifies the construction procedure, improves the construction efficiency, and has the function of melting ice and removing snow.

Description

Technical Field

[0001] This invention relates to a cement repair material, its preparation method and construction method, and more particularly to a magnesium phosphate bead for rapid cement repair, its preparation method and construction method. Background Technology

[0002] Phosphate cement has a long history of use as a repair material in engineering projects due to its rapid setting properties. Magnesium phosphate cement is a type of cementitious material that forms its strength through an acid-base neutralization reaction between alkaline oxides (reburned magnesium oxide) and soluble phosphates. It features rapid setting and hardening, high early strength, good bonding properties, and high biocompatibility, thus being widely used in both civilian and military fields. In the civilian sector, magnesium phosphate cement is mainly used to repair highways, bridges, and airport access roads. Simultaneously, magnesium phosphate cementitious materials are widely used in artificial teeth and bones due to their excellent biocompatibility. In the military sector, magnesium phosphate cement, with its rapid hardening and early strength characteristics, is used for military emergency repairs and construction.

[0003] When using magnesium phosphate cement concrete to repair roads, the inherent early-setting properties of magnesium phosphate necessitate completion of the repair within a relatively short timeframe. Furthermore, the complex composition of magnesium phosphate repair materials makes it easy for workers to make mistakes when weighing and mixing materials on-site within a short period, resulting in the repaired pavement failing to meet expected performance standards. Additionally, for construction workers, a simpler construction procedure generally leads to a lower error rate.

[0004] Therefore, a simple and quick-applied magnesium phosphate repair material is urgently needed for current road repairs. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide magnesium phosphate granules for emergency repair cement that can quickly repair and has a good repair effect;

[0006] A second objective of this invention is to provide a method for preparing the aforementioned magnesium phosphate beads for emergency repair cement.

[0007] A third objective of this invention is to provide a method for emergency repair using the aforementioned magnesium phosphate beads.

[0008] Technical Solution: The magnesium phosphate granules for emergency repair cement that can melt ice and remove snow, as described in this invention, are characterized by comprising a PVA water-soluble film and contents encapsulated within the PVA water-soluble film. The contents, by mass, comprise the following components: 2-3 parts of reburned magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.15-0.25 parts of retarder, 0.3-0.6 parts of acrylamide, 0.03-0.06 parts of ammonium persulfate initiator, and 3.98-4.41 parts of fine aggregate.

[0009] The magnesium-to-phosphorus mass ratio M / P is 2-3; the boron-to-magnesium mass ratio B / M is 0.06-0.10.

[0010] The PVA water-soluble film is made of polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, polyacrylic acid, maleic acid / acrylic acid copolymer, starch, gelatin, xanthan gum, guar gum, hydroxypropyl methylcellulose, and one or more of the above homopolymers, copolymers, or modified components.

[0011] The phosphate is ammonium dihydrogen phosphate with a purity of 98%; the recalcined magnesium oxide is obtained by grinding magnesium oxide after calcination at 1600-1700℃; the particle size range of the ground recalcined magnesium oxide is 0.688-248.9μm; and the retarder is borax.

[0012] The preparation method of the above-mentioned emergency repair cement for melting ice and snow, using magnesium phosphate beads, includes the following steps:

[0013] (A1) Weigh out the calcined magnesium oxide powder, phosphate, retarder, acrylamide, ammonium persulfate and fine aggregate according to the proportion, stir and mix to obtain a mixture;

[0014] (A2) The mixture was coated with PVA water-soluble film according to different mass parts to obtain magnesium phosphate beads of corresponding specifications.

[0015] In step (A1), the mixture is dry-mixed in a mixer at a speed of 60 rpm / min for 60-80 seconds to ensure that the components are packed as tightly as possible to obtain a mixture.

[0016] In step (A2), the mixture is divided into five specifications by mass: 1 part, 5 parts, 10 parts, 20 parts, and 100 parts. The five specifications of granules are mixed and bagged in a ratio of 58:13:6:7:16 from smallest to largest. Specifically, the mixture is divided into five specifications by mass: 1g, 5g, 10g, 20g, and 100g. After being coated with a PVA water-soluble film, the resulting magnesium phosphate granules correspond to five models.

[0017] The construction method for emergency repair cement-based magnesium phosphate beads for melting ice and snow includes the following steps:

[0018] (B1) Clean the repaired area;

[0019] (B2) Determine the total amount of magnesium phosphate cement concrete required based on the area of ​​the repaired area, and then determine the mass of magnesium phosphate beads and water.

[0020] (B3) Steel sheets are placed at intervals in the repair area and wires are buried. One end of the wire is connected to the steel sheet and the other end is connected to the power supply for de-icing and snow removal.

[0021] (B4) First, weigh the mass m0 of the bagged magnesium phosphate beads. Then, pour the required amount of bagged magnesium phosphate beads into the space to be repaired. The highest point of the beads should be tangent to or slightly higher than the upper surface of the space to be repaired. Weigh the remaining mass m1 of the magnesium phosphate beads in the bag. Then, the amount of magnesium phosphate beads used is m0-m1. Add the required amount of water according to the amount used. The PVA water-soluble membrane gradually dissolves in the water, and the components inside the membrane react to complete the repair.

[0022] The proportions and sizes of the magnesium phosphate beads conform to the following formula, thereby achieving close packing:

[0023]

[0024] Wherein, P(D): the percentage of total solids smaller than particle size D; D: the particle size of other condensates; D min Take 0.1mm; D max : refers to the maximum particle size in the system; q: distribution coefficient, taken as 0.23.

[0025] The five specifications of magnesium phosphate beads of this invention can meet all dosage requirements. During construction, the five different specifications of magnesium phosphate beads can be reasonably combined to achieve close packing. While ensuring that the compressive strength is not lower than that of traditional magnesium phosphate cement repair materials, the flexural strength, toughness and workability of the hardened matrix can be improved. Among the five specifications, the smaller ones are fine beads and the larger ones are coarse beads. Fine beads have a good filling effect and can fill the pores of coarse beads, reduce porosity, improve pore structure and thus achieve uniform distribution. The proportion and size of the beads must meet certain requirements to achieve close packing. As shown in formula (1), during construction, the particle size of the beads is continuously distributed. In the model describing this distribution, the Dinger-Funk model is used as an example. This model considers both the maximum and minimum particle size in the actual system and is more consistent with the actual situation. When the value of q is 0.23, the beads can be regarded as achieving the most compact packing. That is, using magnesium phosphate repair beads with different dosages can ensure the maximum density packing during construction.

[0026] In step (B3), the specific process for melting ice and removing snow is as follows:

[0027] (C1) Connect the pre-buried wires to the power supply. The voltage depends on the spacing between the steel sheets and the required efficiency of de-icing and snow removal.

[0028] (C2) When the power is turned on, as the current flows in, the magnesium phosphate hardened matrix gradually heats up, and the heat is conducted to the ice and snow, causing the ice and snow to gradually melt.

[0029] (C3) After the ice and snow have melted to a reasonable level, turn off the power.

[0030] In step (B3), the spacing between the steel sheets is preferably 10-40cm. The spacing width depends on the voltage strength of the electrical equipment used. When the distance between the steel sheets increases, the efficiency of subsequent de-icing and snow removal may be prolonged.

[0031] In step (B4), self-leveling can be achieved without stirring, and the outer membrane of the condensate will gradually dissolve in water, allowing the components inside the membrane to begin reacting.

[0032] In step (B4), the required weight ratio of water to cementitious material, i.e., the water-cement ratio W / B, is 0.20-0.25.

[0033] Under conditions of 20℃ and 50% humidity, the cement matrix can harden within 15-20 minutes, with a compressive strength of not less than 25MPa and a bond strength of not less than 5MPa after 2 hours. When the temperature is lower than the recommended value, the reaction process may be prolonged.

[0034] The de-icing and snow removal efficiency of the in-situ polymerized polyacrylamide magnesium phosphate hardened matrix is ​​related to many factors, including operating temperature, ice and snow thickness, power supply voltage, and current type. Generally, the resistivity of the in-situ polymerized polyacrylamide magnesium phosphate matrix prepared by this method is between 80 Ω·cm and 400 Ω·cm after 28 days of curing.

[0035] In step (C2), under conditions of 20°C and 50% humidity, the time required for a 2cm×2cm×1cm polymeric polyacrylamide magnesium phosphate matrix to completely melt a 1cm×1cm×1cm cube of ice at -15°C on top of it under the action of a 30V DC current at both ends is approximately 8 minutes and 15 seconds. When external conditions and specimen size change, the reaction time may vary.

[0036] Invention Principle: This invention utilizes the rapid hardening properties of magnesium phosphate cement and the in-situ polymerization of acrylamide monomers within the cement matrix under the initiator of ammonium persulfate. Five different types of hydrogel beads are formed by encapsulating a uniformly mixed powder material in a specified proportion using water-soluble PVA material. The proportions of different mass hydrogel beads are designed using close packing theory and then packaged according to these proportions. For use, simply clean the cement surface to be repaired, fill the area with the bagged hydrogel repair material, and add water according to the specified proportion. The water-soluble PVA film dissolves first upon adding water. Once dissolved, the internal powder material reacts with water; magnesium oxide reacts with phosphate to form struvite, etc. Simultaneously, acrylamide monomers polymerize under the initiation of ammonium persulfate to form polyacrylamide, which is uniformly distributed within the hardened matrix. The polyacrylamide forms ion and water pathways within the magnesium phosphate matrix, reducing the overall resistivity. A current path can be formed by applying a potential difference between the two ends. Under Joule heating, the hardened matrix itself heats up, achieving the effect of melting ice and removing snow.

[0037] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) It overcomes the shortcomings of existing magnesium phosphate materials in the field of cement concrete, especially in the field of cement concrete pavement repair technology. It uses calcined magnesium oxide powder, phosphate, retarder, acrylamide and fine aggregate as the main body, and uses PVA water-soluble film to package the above materials into a variety of fixed dosage magnesium phosphate repair beads. The PVA material used in the outer film of the beads does not dissolve or leak in the room temperature and waterless environment, and does not crack in the dry environment. It can dissolve in a short time after encountering water and leaves no residue, making the raw materials more uniform and forming a network structure inside the matrix, increasing the toughness of the hardened matrix. Magnesium phosphate polymerizes polyacrylamide in situ during service, which has the function of melting ice and removing snow. It can complete the melting ice and removing snow by simply turning on the power. The process can be repeated and has basically no pollution to the environment, avoiding the corrosion and pollution of cement pavement or underlying soil by melting ice salt. (2) During construction, there is no need for pre-mixing, stirring, or pouring. Simply place a certain amount of magnesium phosphate beads at the location to be repaired according to the actual project, and then add a certain amount of water. After the repair beads dissolve, react, and harden, they can achieve self-leveling, which greatly simplifies the construction procedure of magnesium phosphate road repair technology and improves on-site construction efficiency. (3) Using magnesium phosphate repair beads for repair is simple and convenient to operate. At the same time, it isolates materials and construction personnel, which reduces the emission of polluting gases such as ammonia and is beneficial to the health of construction personnel. Attached Figure Description

[0038] Figure 1 This is a scanning electron microscope image of recalcined magnesium oxide from Example 1;

[0039] Figure 2 This is a particle size distribution diagram of the reburned magnesium oxide from Example 1;

[0040] Figure 3 Thermogravimetric analysis diagram of the hardened matrix in Example 1;

[0041] Figure 4 The image shows the XRD pattern of the hardened matrix in Example 1. Detailed Implementation

[0042] The present invention will now be described in further detail.

[0043] Example 1

[0044] A magnesium phosphate rapid repair material suitable for emergency repairs and snow / ice melting is disclosed, namely magnesium phosphate repair beads, comprising contents and a PVA water-soluble film. The contents include 2.5 parts of recalcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.15 parts of borax, 0.3 parts of acrylamide, 0.03 parts of ammonium persulfate initiator, and 3.98 parts of fine aggregate. The magnesium-to-phosphorus mass ratio (M / P) is 2.5, the boron-to-magnesium mass ratio (B / M) is 0.06, and the binder-to-mortar ratio is 1:1. In this embodiment, the water-to-cement weight ratio (W / B) required for construction is 0.20. The magnesium oxide was purchased from Dashiqiao Jubo High-Temperature Refractory Materials Business Department, model Ms92; this magnesium oxide material is obtained by dry mining and purification of magnesite ore, followed by calcination at 1650℃ and grinding to produce recalcined magnesium oxide; the dry process used is existing technology.

[0045] Figure 1 , 2 The images show the morphology and particle size distribution of calcined and recalcined magnesium oxide after crushing in a ball mill. The particle size distribution of magnesium oxide is conducive to a complete reaction, preventing it from reacting too quickly. Figure 3 The thermogravimetric curve shows that the green curve drops significantly before 100℃, indicating the formation of a large number of struvite crystals that are beneficial to the overall strength; from Figure 4 The XRD pattern shows that the matrix after the reaction still contains a large amount of recalcined magnesium oxide, as well as the main reaction products struvite and dittmarite. No unreacted ammonium dihydrogen phosphate was found, indicating that the substances inside the beads reacted completely. Specifically, struvite is composed of NH4MgPO46H2O, and dittmarite is composed of NH4MgPO4H2O.

[0046] The preparation method of the agglomerates is as follows:

[0047] S1. Dry material mixing: At the prefabrication plant, weigh and mix the above-mentioned proportions of calcined magnesium oxide powder, ammonium dihydrogen phosphate, borax, acrylamide, APS, and fine aggregates, and then dry mix them in a mixer at a speed of 60 rpm / min for 80 seconds to make them uniform and obtain the mixture.

[0048] S2. Weigh the mixture according to five dosages: 1g, 5g, 10g, 20g, and 100g, ensuring close distribution. Encapsulate the mixture with a PVA water-soluble film to form five fixed dosages of magnesium phosphate repair beads: 1g, 5g, 10g, 20g, and 100g. These five types can meet all usage requirements. Furthermore, the different dosages of magnesium phosphate repair beads ensure maximum density packing during construction, i.e., close packing. The proportion and size of the magnesium phosphate beads conform to the formula (1) above, thus achieving close packing:

[0049]

[0050] V: Volume of the agglomerate;

[0051] R: radius of the condensate;

[0052] m=ρV

[0053] m: Mass of the mixture; the weight of PVA is ignored;

[0054] ρ: The average density of the mixture is taken as 2.85 g / cm³. 3 ;

[0055] Where D = d + 2x, and x is the thickness of the PVA water-soluble film, which is 0.01 cm.

[0056] Table 1

[0057]

[0058] The on-site construction method for magnesium phosphate repair beads is as follows:

[0059] S1. Use brushes and other tools to thoroughly clean the pit and crack area, ensuring the repair area is clean and dry;

[0060] S2. Determine the total amount of magnesium phosphate cement concrete required based on the area to be repaired, and obtain the mass of magnesium phosphate repair beads and water respectively; first, place steel plates at 40cm intervals in the repair area and embed wires, with one end of the wire connected to the steel plate and the other end connected to an AC power source; then pour the required beads directly onto the area to be repaired, and then pour in the calculated amount of water. Under the conditions of 20℃ and 50% humidity, the cement matrix will harden within 20 minutes, with a compressive strength of not less than 25MPa, a bond strength of not less than 5MPa, a flexural strength of not less than 7MPa, and a resistivity of less than 400Ω·cm after 2 hours. When the temperature is lower than the recommended value, the reaction process may be prolonged.

[0061] S3. The material can achieve self-leveling without stirring. The outer membrane of the beads will gradually dissolve in water, and the components inside the membrane can begin to react.

[0062] S4. After the material has hardened, it can be used for de-icing and snow removal after spraying water for 1 day. After powering on, the snow melting rate of the repaired section is significantly greater than that of the unrepaired section. Within 30 minutes, all the snow in the repaired section and a certain area around it will evaporate. When the outside temperature is lower than the recommended value, the de-icing and snow removal process may be prolonged.

[0063] Example 2

[0064] A magnesium phosphate cement concrete repair material suitable for emergency repairs, namely magnesium phosphate repair beads, comprising contents and a PVA water-soluble film.

[0065] The contents include 2.5 parts of calcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.25 parts of borax, 0.6 parts of acrylamide, 0.06 parts of APS, and 4.41 parts of fine aggregate.

[0066] The M / P mass ratio in the contents is 2.5, and the B / M mass ratio is 0.10.

[0067] In this embodiment, the weight ratio of water to cementitious material required for construction, i.e., the water-cement ratio W / B, is 0.25.

[0068] The preparation method of magnesium phosphate repair beads is as follows:

[0069] S1. Dry material mixing: Weigh and mix the above-mentioned proportions of calcined magnesium oxide powder, potassium dihydrogen phosphate, borax, acrylamide, APS, and fine aggregate. Dry mix them in a mixer at 60 rpm / min for 60-80 seconds to ensure uniform mixing and that the components are packed as tightly as possible to obtain the mixture.

[0070] S2. Weigh the mixture according to five dosages of 1g, 5g, 10g, 20g, and 100g, ensure they are tightly distributed, and encapsulate them with a PVA water-soluble film to form five fixed dosages of magnesium phosphate repair beads of 1g, 5g, 10g, 20g, and 100g. At this point, due to the increased dosage of acrylamide and ammonium persulfate, the overall density of the mixture is lower than the theoretically calculated value, but the error is very small, so the 58:13:6:7:16 ratio is still used for bagging.

[0071] This results in a simple-to-apply magnesium phosphate quick-repair material, namely magnesium phosphate repair beads. These five models can meet all dosage requirements. Furthermore, the different dosages of magnesium phosphate repair beads ensure maximum density packing during application, i.e., tight packing. The on-site application method for magnesium phosphate repair beads is as follows:

[0072] S1. Use brushes and other tools to thoroughly clean the pit and crack area, ensuring the repair area is clean and dry;

[0073] S2. Determine the total amount of magnesium phosphate cement concrete required based on the area to be repaired, and obtain the mass of magnesium phosphate repair beads and water respectively; first, pour the required beads directly onto the area to be repaired, then pour in the calculated amount of water. Under the conditions of 20℃ and 50% humidity, the cement matrix will harden within 20 minutes. The compressive strength after 2 hours is not less than 25MPa, the bond strength is not less than 5MPa, the flexural strength is not less than 9MPa, and the resistivity is less than 300Ω·cm. When the temperature is lower than the recommended value, the reaction process may be prolonged.

[0074] S3. The material can achieve self-leveling without stirring. The outer membrane of the beads will gradually dissolve in water, and the components inside the membrane can begin to react.

[0075] Example 3

[0076] Based on Example 1, the difference from Example 1 is that the contents contain 3 parts of calcined magnesium oxide and the M / P mass ratio in the contents is 3.

[0077] Example 4

[0078] Based on Example 1, the difference from Example 1 is that the contents contain 2 parts of calcined magnesium oxide and the M / P mass ratio in the contents is 2.

[0079] Comparative Example 1

[0080] Ordinary magnesium phosphate cement concrete repair material, with the addition of acrylamide monomer and ammonium persulfate, does not form magnesium phosphate repair beads.

[0081] The contents include 2.5 parts of calcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.15 parts of borax, 0.3 parts of acrylamide, 0.03 parts of ammonium persulfate initiator, and 3.98 parts of fine aggregate.

[0082] The magnesium-to-phosphorus ratio (M / P) in the contents is 2.5, the boron-to-magnesium ratio (B / M) is 6%, and the mortar ratio is 1:1.

[0083] The weight ratio of water to cementitious material required during construction, i.e., the water-cement ratio W / B, is 0.20.

[0084] The on-site construction method for the above-mentioned ordinary magnesium phosphate cement concrete repair material is as follows:

[0085] S1. Use brushes and other tools to thoroughly clean the pit and crack area, ensuring the repair area is clean and dry;

[0086] S2. Determine the total amount of magnesium phosphate cement concrete required based on the area to be repaired. According to the specified mix proportion, obtain the mass of each raw material and water in the magnesium phosphate cement concrete repair material. Weigh each raw material of the repair material and put it into the mixing pot. First, slowly stir at 60 rpm / min for 20 seconds. While slowly stirring, add the required water to the mixer. Then, quickly stir at 300 rpm / min for 90 seconds to make the material have good fluidity and uniformity. Pour the material within 10 minutes.

[0087] S3. After injecting magnesium phosphate cement mortar into the repair area, tamp it down to make it compact, and then scrape the surface smooth.

[0088] S4. The hardened substrate after repair has a high resistivity and does not have the ability to melt ice and remove snow.

[0089] Comparative Example 2

[0090] Magnesium phosphate repair beads contain magnesium phosphate repair material and PVA water-soluble film, without added acrylamide monomer and ammonium persulfate.

[0091] Ordinary magnesium phosphate repair beads contain 2.5 parts of calcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.15 parts of borax, and 3.65 parts of fine aggregate.

[0092] The magnesium-to-phosphorus ratio (M / P) in the contents is 2.5, the boron-to-magnesium ratio (B / M) is 6%, and the mortar ratio is 1:1.

[0093] The weight ratio of water to cementitious material required during construction, i.e., the water-cement ratio W / B, is 0.20.

[0094] The preparation method of the above-mentioned ordinary magnesium phosphate cement repair beads is as follows:

[0095] S1. Dry material mixing: At the prefabrication plant, weigh and mix the above-mentioned proportions of calcined magnesium oxide powder, ammonium dihydrogen phosphate, borax, acrylamide, APS, and fine aggregates, and then dry mix them in a mixer at a speed of 60 rpm / min for 80 seconds to make them uniform and obtain the mixture.

[0096] S2. Weigh the mixture according to five dosages of 1g, 5g, 10g, 20g, and 100g, ensure that it is tightly distributed, and encapsulate it with a PVA water-soluble film to form five fixed dosages of magnesium phosphate repair beads of 1g, 5g, 10g, 20g, and 100g, and bag them in a ratio of 58:13:6:7:16.

[0097] The on-site construction method for repairing the above-mentioned ordinary magnesium phosphate cement beads is as follows:

[0098] S1. Use brushes and other tools to thoroughly clean the pit and crack area, ensuring the repair area is clean and dry;

[0099] S2. Based on the area of ​​the repair area, determine the total amount of magnesium phosphate cement concrete required, obtain the mass of magnesium phosphate repair beads and water respectively, then pour the required beads directly onto the area to be repaired, and then pour in the calculated amount of water;

[0100] S3. The material can achieve self-leveling without stirring. The outer membrane of the beads will gradually dissolve in water, and the components inside the membrane can begin to react.

[0101] Comparative Example 3

[0102] Single-size magnesium phosphate repair beads, comprising magnesium phosphate repair material, acrylamide and ammonium persulfate, and PVA water-soluble film.

[0103] The raw material for single-size magnesium phosphate repair beads includes 2.5 parts of calcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.25 parts of borax, 0.6 parts of acrylamide, 0.06 parts of APS, and 4.41 parts of fine aggregate.

[0104] The magnesium-to-phosphorus ratio (M / P) in the contents is 2.5, the boron-to-magnesium ratio (B / M) is 6%, and the mortar ratio is 1:1.

[0105] The weight ratio of water to cementitious material required during construction, i.e., the water-cement ratio W / B, is 0.25.

[0106] The preparation method of the above-mentioned ordinary magnesium phosphate cement concrete repair material repair beads is as follows:

[0107] S1. Dry material mixing: At the prefabrication plant, weigh and mix the above-mentioned proportions of calcined magnesium oxide powder, ammonium dihydrogen phosphate, borax, acrylamide, APS, and fine aggregates, and then dry mix them in a mixer at a speed of 60 rpm / min for 80 seconds to make them uniform and obtain the mixture.

[0108] S2. Divide the mixture into several small portions of 10g each, encapsulate them with PVA water-soluble film, and pack them into bags for later use.

[0109] The on-site construction method for the above-mentioned single-size magnesium phosphate cement repair beads is as follows:

[0110] S1. Use brushes and other tools to thoroughly clean the pit and crack area, ensuring the repair area is clean and dry;

[0111] S2. Based on the area of ​​the repair area, determine the total amount of magnesium phosphate cement concrete required, obtain the mass of magnesium phosphate repair beads and water respectively, then pour the required beads directly onto the area to be repaired, and then pour in the calculated amount of water;

[0112] S3. The material can achieve self-leveling without stirring. The outer membrane of the beads will gradually dissolve in water, and the components inside the membrane can begin to react.

[0113] Performance and construction experience testing

[0114] 1. Performance Testing

[0115] The setting time, strength, and resistivity of the magnesium phosphate repair beads prepared in Examples 1 and 2 at different ages were tested and compared with the repair materials of Comparative Examples 1, 2, and 3, as follows:

[0116] The magnesium phosphate repair beads obtained in the examples were prepared into magnesium phosphate cement mortar according to step S2 of the corresponding construction method. The setting time of the magnesium phosphate repair material was tested using a Vicat apparatus, and the mechanical and electrical properties of the magnesium phosphate repair material were tested using a standard mold. The specimen size was 40mm*40mm*160mm. Similarly, the ordinary magnesium phosphate cement mortar repair material of the comparative example was prepared and pressed into specimens according to step S2 of the corresponding construction method. The specimens were demolded after about 1 hour and cured in an indoor natural environment, i.e., 20℃ and 50% humidity, for 2 hours, 3 days, and 28 days. The compressive strength, flexural strength, setting time, and resistivity were tested. The curing temperature was 20℃. The test results are shown in Table 2.

[0117] Table 2 Performance tests of each embodiment and comparative example

[0118]

[0119] Comparative Example 1 corresponds to Example 1. Except for the absence of a water-soluble PVA membrane, the other material components and proportions are exactly the same. Due to the lack of a water-soluble membrane, the materials in Comparative Example 1 reacted rapidly, resulting in a short setting time and a lack of an engineering window, which is not conducive to engineering use. However, there is no significant difference in the mechanical properties between Comparative Example 1 and Example 1, although the former has a slightly higher resistivity.

[0120] Comparative Example 2 corresponds to Example 1, except that acrylamide and ammonium persulfate were not added; all other material components and proportions are exactly the same. Because acrylamide and ammonium persulfate were not added, the resistivity of Comparative Example 2 is significantly higher than that of Example 1, meaning the former essentially does not meet the performance requirements for ice melting and snow removal.

[0121] Comparative Example 3 corresponds to Example 2, except that it uses only magnesium phosphate beads of a single particle size; the other material components and mixing ratios are exactly the same. Using beads of a single particle size cannot meet the construction requirements; after watering, large-scale collapse occurs, and the mechanical strength decreases significantly, failing to meet the engineering strength requirements.

[0122] Compared with Example 1, Example 2 shows that due to the increased dosage of acrylamide and ammonium persulfate, the setting time is reduced, the flexural strength of the hardened matrix is ​​improved, the resistivity is reduced, and the ice-melting efficiency is increased.

[0123] 2. Construction Experience

[0124] The magnesium phosphate repair beads prepared in Examples 1 and 2 were subjected to field tests and compared with those of the comparative examples. Specifically, a cement road in Jiangning District, Nanjing City, Jiangsu Province was selected. This road has low traffic volume, but due to years of neglect, it has many defects. Four small potholes with similar locations, vehicle loads, and shapes and sizes of defects were selected as repair targets and labeled Xa, Xb, Xc, and Xd. Repair work was carried out at Xa, Xb, Xc, and Xd using methods from Examples 1, 2, 1, 2, and 3, respectively. The experimental results are shown in Table 3.

[0125] Table 3 Construction Experience of Each Example and Comparative Example

[0126] Construction time Construction effect Construction experience Example 1 5’10” 1.1 95 Example 2 5’06” 1.3 94 Comparative Example 1 8’25” 1 80 Comparative Example 2 15’45” 1.2 69 Comparative Example 3 15’30” 0.4 60

[0127] The construction effect is based on the 28-day construction effect of Comparative Example 1, and is set as unit 1. The higher the construction effect value, the better the construction effect.

[0128] The construction experience score is calculated out of 100. Five to six construction workers participating in the on-site test each gave a score based on the construction process, and the average score was rounded down.

[0129] Compared to Example 1, Example 2 increased the amount of ammonium persulfate and acrylamide, while the other steps remained the same, resulting in similar construction effects. Example 2, with its faster setting speed, slightly improved repair efficiency. Comparative Example 2 corresponds to Example 1, except that the preparation process of magnesium phosphate repair beads was omitted, and the material composition ratio was exactly the same. However, the absence of PVA beads in Comparative Example 2 led to an excessively fast reaction rate in the magnesium phosphate composite material, limiting repairs to a small area and requiring multiple cement preparations, thus increasing the construction steps. Compared to Comparative Example 2, Example 1, by using PVA beads, eliminated the need for on-site preparation of magnesium phosphate cement, making construction more convenient. Comparative Example 3 showed significantly lower construction effects and user experience compared to other groups, primarily because it failed to meet the flatness and strength requirements during construction, necessitating secondary repairs. Table 3 shows that the construction time for all examples was shorter than that for the comparative examples; except for Comparative Example 3, the construction effects were similar, with the examples being superior to the comparative examples; the user experience for the examples was also better than that for the comparative examples. This indicates that the in-situ polymerized polyacrylamide magnesium phosphate repair beads prepared by this invention are more convenient to use in actual construction than ordinary magnesium phosphate cement concrete repair materials, showing significant advantages.

Claims

1. A magnesium phosphate bead for emergency repairs that can melt ice and remove snow, characterized in that, The product comprises a water-soluble membrane and contents encapsulated within the water-soluble membrane. The contents, by mass, comprise the following components: 2-3 parts of calcined magnesium oxide, 1 part of ammonium dihydrogen phosphate, 0.15-0.25 parts of retarder, 0.3-0.6 parts of acrylamide, 0.03-0.06 parts of ammonium persulfate initiator, and 3.98-4.41 parts of fine aggregate. The water-soluble membrane is made of one or more of the following: polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, polyacrylic acid, maleic acid / acrylic acid copolymer, starch, gelatin, xanthan gum, guar gum, and hydroxypropyl methylcellulose.

2. The magnesium phosphate beads for emergency repair and de-icing / snow removal according to claim 1, characterized in that, The magnesium-to-phosphorus mass ratio (M / P) is 2-3; the retarder is borax, and the boron-to-magnesium mass ratio (B / M) is 0.06-0.

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3. The magnesium phosphate beads for emergency repair and de-icing / snow removal according to claim 1, characterized in that, The recalcined magnesium oxide is obtained by grinding magnesium oxide after calcination at a temperature of 1600-1700℃.

4. A method for preparing magnesium phosphate beads for emergency repair and de-icing / snow removal as described in claim 1, characterized in that, Includes the following steps: (A1) Weigh out the calcined magnesium oxide powder, ammonium dihydrogen phosphate, retarder, acrylamide, ammonium persulfate and fine aggregate according to the proportion, stir and mix to obtain a mixture; (A2) The mixture was coated with a water-soluble film according to different mass parts to obtain magnesium phosphate beads of corresponding specifications.

5. The method for preparing magnesium phosphate beads for emergency repair and de-icing / snow removal according to claim 4, characterized in that, In step (A2), the mixture is divided into five specifications by mass: 1 part, 5 parts, 10 parts, 20 parts and 100 parts. The five specifications of agar beads are mixed and bagged in a ratio of 58:13:6:7:16 from smallest to largest.

6. The method for preparing magnesium phosphate beads for emergency repair and de-icing / snow removal according to claim 4, characterized in that, In step (A2), the mixture is divided into five specifications by mass: 1g, 5g, 10g, 20g and 100g.

7. A method for constructing magnesium phosphate beads for emergency repairs and de-icing / snow removal as described in claim 1, characterized in that, Includes the following steps: (B1) Clean the repair area; (B2) Determine the total amount of magnesium phosphate cement concrete required based on the area of ​​the repaired area, and then determine the mass of magnesium phosphate beads and water; (B3) Steel sheets are placed at intervals in the repair area and wires are buried. One end of the wire is connected to the steel sheet and the other end is connected to the power supply for de-icing and snow removal. (B4) First, weigh the mass m0 of the bagged magnesium phosphate beads. Then, pour the bagged magnesium phosphate beads into the space to be repaired. The highest point of the beads should be tangent to or slightly higher than the upper surface of the space to be repaired. Weigh the mass m1 of the remaining magnesium phosphate beads in the bag. The amount of magnesium phosphate beads used is m0 - m1. Add the required amount of water according to the amount used. The water-soluble membrane gradually dissolves in the water, and the components inside the membrane react to complete the repair.

8. The construction method of magnesium phosphate beads for emergency repairs and de-icing / snow removal according to claim 7, characterized in that, In step (B4), the required weight ratio of water to cementitious material, i.e., the water-cement ratio W / B, is 0.20-0.

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9. The construction method of magnesium phosphate beads for emergency repairs and de-icing / snow removal according to claim 7, characterized in that, The proportions and sizes of the magnesium phosphate beads conform to the following formula (1), thereby achieving close packing: （1） in, The percentage of particles smaller than diameter D in the total solids; Other bead sizes; Take 0.1mm; : Refers to the maximum particle size in the system; Distribution coefficient, taken as 0.23.

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