A magnesium phosphate-based cement grouting material, a preparation method and application thereof

Abstract

The application discloses a magnesium phosphate-based cement grouting material and a preparation method and application thereof. The raw materials of the magnesium phosphate-based cement grouting material include A component and B component; the raw materials of the A component include, in parts by weight, calcined magnesium oxide 140-200 parts, bentonite 0-30 parts, hydroxypropyl methylcellulose 0.2-0.5 parts, an additive 1-10 parts and water 70-140 parts; the raw materials of the B component include a first dihydrogen phosphate 70-100 parts, pretreated high-molecular water-absorbing resin 20-50 parts, sodium polyacrylate 0.5-2 parts and water 30-70 parts; the pretreated high-molecular water-absorbing resin is obtained by soaking the high-molecular water-absorbing resin in an aqueous solution of a second dihydrogen phosphate. The magnesium phosphate-based cement grouting material has the characteristics of low shrinkage, short and adjustable setting time, high compressive strength, simple construction, low cost, green environmental protection, good grout injection, good water dispersion resistance, good durability in a long-term soaking environment and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of grouting materials, in particular to a magnesium phosphate-based cement grouting material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of China's economy and the shortage of land resources, underground engineering construction is developing rapidly. Leakage is prone to occur in underground engineering construction represented by tunnels and stations, which endangers the safety, stability, durability of the building (structure) and affects the normal use function, resulting in huge operation and maintenance costs. Underground engineering leakage can be divided into slow seepage, fast seepage, leakage and gushing according to the flow rate. Among them, leakage, especially strong leakage, is the most serious. On the project, epoxy resin, cement, cement-silicate materials and other materials are usually used to form a gel structure for grouting and plugging. However, the epoxy resin material has high cost, poor environmental friendliness and poor resistance to water erosion; the ordinary cement-based grouting material has long setting time, poor water dispersion resistance and complex construction; the cement-silicate material has short gel time and high strength, but poor durability in long-term water soaking environment.

[0003] Chinese patent CN 117865593 A discloses a new water-rich stratum green anti-dispersion synchronous grouting material and a preparation method thereof, which is composed of the following components according to specific weight fractions: Portland cement, fine sand, fly ash, hydroxypropyl methyl cellulose, 2-ethylhexyl phosphate-2-ethylhexyl ester, sodium tripolyphosphate, sodium dodecyl sulfate, polycarboxylic acid superplasticizer or naphthalene superplasticizer, polyacrylamide, formic acid, bentonite and water. However, the product has a long setting time of 5 hours, which is not suitable for use as a rapid rescue and repair material for water leakage cracks. Chinese patent CN 108002802 A discloses a phosphorus-magnesium-based cement grouting material and a preparation method, which is composed of the following components according to specific weight fractions: composite magnesium compound, composite retarder, water reducing agent, acid-base buffer, composite stabilizer, composite surfactant, phosphate and defoaming agent. However, the material has a small water-cement ratio, which is not suitable for grouting and water plugging in small cracks.

[0004] Therefore, it is of great significance to develop a water leakage crack repair material with short and adjustable setting time, high compressive strength, simple construction, low cost, green environmental protection, good grout injection, good water dispersion resistance and good durability in long-term water soaking environment. SUMMARY

[0005] The present application aims to overcome the above technical deficiencies and proposes a magnesium phosphate-based cement grouting material and a preparation method and application thereof, which solve the technical problems of long setting time, poor water dispersion resistance, complex construction and poor durability in long-term water soaking environment of inorganic grouting materials in the prior art.

[0006] In a first aspect, the present application provides a magnesium phosphate-based cement grouting material, raw materials of which include A component and B component; wherein, in terms of parts by weight, raw materials of the A component include: calcined magnesium oxide 140-200 parts, bentonite 0-30 parts, hydroxypropyl methyl cellulose 0.2-0.5 parts, additive 1-10 parts and water 70-140 parts; raw materials of the B component include: first dihydrogen phosphate salt 70-100 parts, pretreated high molecular water-absorbing resin 20-50 parts, sodium polyacrylate 0.5-2 parts and water 30-70 parts; the pretreated high molecular water-absorbing resin is obtained by soaking the high molecular water-absorbing resin in an aqueous solution of second dihydrogen phosphate salt; the molar ratio of magnesium to phosphorus in the calcined magnesium oxide and the first dihydrogen phosphate salt is (5.5-6.5): 1.

[0007] In a second aspect, the present application provides a preparation method of a magnesium phosphate-based cement grouting material, which includes the following steps:

[0008] The calcined magnesium oxide, the bentonite and the hydroxypropyl methyl cellulose are mixed uniformly to obtain a mixed powder; the additive and the water are mixed uniformly to obtain a mixed liquid; the mixed powder and the mixed liquid are mixed uniformly to obtain the A component;

[0009] The first dihydrogen phosphate salt, the sodium polyacrylate, the pretreated high molecular water-absorbing resin and the water are mixed uniformly to obtain the B component.

[0010] In a third aspect, the present application provides an application of a magnesium phosphate-based cement grouting material, which is applied to leakage water crack plugging.

[0011] Compared with the prior art, the present application has the following beneficial effects:

[0012] The magnesium phosphate-based cement grouting material of the present application has the characteristics of low shrinkage, short and adjustable setting time, high compressive strength, simple construction, low cost, green environmental protection, good grouting property, good water dispersion resistance and good durability in long-term water soaking environment. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0014] In a first aspect, the present application provides a magnesium phosphate-based cement grouting material, raw materials of which include A component and B component; wherein, in terms of weight parts, raw materials of the A component include: calcined magnesium oxide 140-200 parts, bentonite 0-30 parts, hydroxypropyl methyl cellulose 0.2-0.5 parts, additive 1-10 parts, and water 70-140 parts; and raw materials of the B component include: first dihydrogen phosphate salt 70-100 parts, pretreated high molecular water-absorbing resin 20-50 parts, sodium polyacrylate 0.5-2 parts, and water 30-70 parts.

[0015] The roles of the main raw materials used in the present application are as follows:

[0016] Calcined magnesium oxide and ammonium dihydrogen phosphate: the two react to form the cementing phase struvite, which, together with the heavy-burned magnesium oxide (aggregate role), provides strength; the magnesium oxide is both a raw material for forming the cementing phase struvite and an aggregate of magnesium phosphate (MPC) cement; the light-burned magnesium oxide with a low calcination temperature provides a faster reaction rate, and the heavy-burned magnesium oxide with a high calcination temperature provides the aggregate role;

[0017] Bentonite and hydroxypropyl methyl cellulose: can increase the viscosity of the A component, improve the stability of the A component, and avoid sedimentation;

[0018] Pretreated high molecular water-absorbing resin (SAP): obtained by pre-adsorbing a dihydrogen phosphate salt solution. By using the pretreated SAP, the proportion of the actual dihydrogen phosphate salt can be increased, and an internal curing effect can be achieved; the struvite formed by the reaction between the dihydrogen phosphate salt released in the later stage and the magnesium oxide can fill the voids; the heat released by the reaction between the magnesium oxide and the dihydrogen phosphate salt in the early stage can make the pretreated high molecular water-absorbing resin release the dihydrogen phosphate salt to further participate in the reaction, prolong the total reaction time, and make the reaction relatively mild; the high molecular water-absorbing resin releasing the dihydrogen phosphate salt solution in the later stage can absorb a small amount of water immersed in the interior of the grouting material and expand to fill the voids to some extent, hinder the water transmission, and improve the water erosion resistance of the material.

[0019] Sodium polyacrylate: in an aqueous solution, the molecular chains of sodium polyacrylate can form a network structure, and these molecular chains have a certain cross-linking effect, which can increase the viscosity and improve the water dispersion resistance; at the same time, the molecular chains contain hydrophilic carboxyl functional groups, and these carboxyl groups will produce carboxylate negative ions after being neutralized by alkali, and have good acid and alkali resistance.

[0020] In the present embodiment, the first dihydrogen phosphate salt is at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate, and is preferably ammonium dihydrogen phosphate. Among the above dihydrogen phosphate salts, ammonium dihydrogen phosphate reacts fastest with magnesium oxide, has the highest early strength, can meet the requirements of rapid plugging and provide higher early strength, and is therefore preferred.

[0021] In the embodiment, the pretreated high polymer water-absorbing resin is obtained by soaking the high polymer water-absorbing resin in the aqueous solution of the second dihydrogen phosphate salt.

[0022] The particle size of the high polymer water-absorbing resin is 200-500 mesh, the water absorption rate in pure water is 100-1000 times, and the liquid absorption rate in a 2.5 mol / L dihydrogen phosphate salt solution is 1-50 times.

[0023] The second dihydrogen phosphate salt is at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate. Among the dihydrogen phosphate salts, ammonium dihydrogen phosphate reacts fastest with magnesium oxide, has the highest early strength, can satisfy rapid plugging, and can provide higher early strength, and therefore is preferably ammonium dihydrogen phosphate.

[0024] The concentration of the aqueous solution of the second dihydrogen phosphate salt is 1-5 mol / L, and is further 2.5 mol / L.

[0025] The solid-liquid ratio of the high polymer water-absorbing resin to the aqueous solution of the second dihydrogen phosphate salt is 1:(50-500), and is further 1:100.

[0026] The soaking temperature is 20-30℃, and the soaking time is 10-60 min, and is further 10 min.

[0027] The pretreated high polymer water-absorbing resin is obtained by adsorbing the high polymer water-absorbing resin in the aqueous solution of the second dihydrogen phosphate salt to saturation.

[0028] In the embodiment, the magnesium oxide is at least one of light-burned magnesium oxide or heavy-burned magnesium oxide.

[0029] Preferably, the calcination temperature of the light-burned magnesium oxide is 900-1000℃, and is further 950℃; and the calcination temperature of the heavy-burned magnesium oxide is 1600-1700℃, and is further 1650℃.

[0030] Preferably, the calcined magnesium oxide is compounded from light-burned magnesium oxide and heavy-burned magnesium oxide. Generally, the lower the calcination temperature, the higher the activity of the magnesium oxide, and the faster the magnesium oxide participates in the reaction; the higher the calcination temperature, the higher the strength of the magnesium oxide, and the higher the strength provided by the magnesium oxide as an aggregate. In the compound system of the present application, the light-burned magnesium oxide reacts first and provides strength faster, and when the light-burned magnesium oxide is completely reacted, the heavy-burned magnesium oxide continues to react, and when the dihydrogen phosphate salt is completely reacted, the remaining magnesium oxide is magnesium oxide with a higher calcination temperature, which can provide higher strength to the matrix, and the compound of the two can achieve rapid plugging while achieving relatively high strength.

[0031] More preferably, the mass ratio of the light-burned magnesium oxide to the heavy-burned magnesium oxide is (2-4):1, and is more preferably 3:1.

[0032] In the embodiment, the particle size of the bentonite is 100-300 mesh, and further 200 mesh.

[0033] In the embodiment, the viscosity of the hydroxypropyl methyl cellulose is 100000-300000 mPa·s, and further 200000 mPa·s.

[0034] In the embodiment, the additive includes at least one of a defoaming agent and a water reducing agent.

[0035] The defoaming agent is a silicone defoaming agent, and the solid content is 5%-20%, and further 10%.

[0036] The water reducing agent is a high-efficiency polycarboxylic acid water reducing agent, and the solid content is 30%-50%, and further 40%.

[0037] In the embodiment, the molar ratio of magnesium to phosphorus in the calcined magnesium oxide and the first dihydrogen phosphate salt is (5.5-6.5):1, and further 6:1.

[0038] In the embodiment, the magnesium phosphate-based cement grouting material, in terms of weight parts, the raw materials of the A component include: 170-190 parts of calcined magnesium oxide, 15-20 parts of bentonite, 0.3-0.4 parts of hydroxypropyl methyl cellulose, 3-6 parts of additive, and 100-120 parts of water; the raw materials of the B component include: 80-90 parts of the first dihydrogen phosphate salt, 30-40 parts of the pretreated high-molecular water-absorbing resin, 0.8-1.2 parts of sodium polyacrylate, and 40-60 parts of water.

[0039] In a second aspect, the application provides a preparation method of a magnesium phosphate-based cement grouting material, including the following steps:

[0040] S1, uniformly mixing the calcined magnesium oxide, the bentonite, and the hydroxypropyl methyl cellulose to obtain a mixed powder; uniformly mixing the additive and the water to obtain a mixed liquid; and uniformly mixing the mixed powder and the mixed liquid to obtain the A component;

[0041] S2, uniformly mixing the first dihydrogen phosphate salt, the sodium polyacrylate, the pretreated high-molecular water-absorbing resin, and the water to obtain the B component.

[0042] The application does not limit the order of steps S1 and S2, and a person skilled in the art can select according to the actual situation.

[0043] In the embodiment, the calcined magnesium oxide, the bentonite, and the hydroxypropyl methyl cellulose are uniformly mixed by stirring, and the stirring time is 20-60 s.

[0044] In the embodiment, the additive and the water are uniformly mixed by stirring, and the stirring time is 20-60 s.

[0045] In the embodiment, the mixed powder and the mixed liquid are mixed uniformly by stirring, and the stirring time is 1-5 min.

[0046] In the embodiment, the first dihydrogen phosphate, the sodium polyacrylate, the pretreated high-molecular water-absorbing resin and water are mixed uniformly by stirring, and the stirring time is 0.5-2 min.

[0047] In a third aspect, the application provides an application of the magnesium phosphate-based cement grouting material, and the magnesium phosphate-based cement grouting material is applied to leakage water crack sealing, preferably strong leakage water crack sealing.

[0048] In the embodiment, the application comprises:

[0049] The A component and the B component are mixed uniformly and injected into the leakage water crack for sealing.

[0050] Further, the process of mixing the A component and the B component uniformly comprises: loading the A component and the B component into a double-liquid grouting machine storage bin, and mixing the A component and the B component uniformly by the double-liquid grouting machine.

[0051] To avoid redundancy, in the following examples and comparative examples of the application, some raw materials are summarized as follows:

[0052] Magnesium oxide: both light-burned magnesium oxide and heavy-burned magnesium oxide are provided by Dashiqiao City Juopu High-temperature Refractory Material Operating Department, the light-burned magnesium oxide has a calcination temperature of 950 °C, a specific surface area of 1.62 m 2 / g, and a purity of 85.98%; the heavy-burned magnesium oxide has a calcination temperature of 1650 °C, a specific surface area of 1.35 m 2 / g, and a purity of 89.61%, and the chemical composition is shown in Table 1.

[0053] Table 1 Chemical composition table of magnesium oxide / wt.%

[0054]

[0055] The particle size of the bentonite is 200 mesh;

[0056] The viscosity of the hydroxypropyl methyl cellulose is 200000 mPa·s;

[0057] The defoaming agent is an organic silicon defoaming agent, and the solid content is 10%;

[0058] The water reducing agent is a high-efficiency polycarboxylic acid water reducing agent, and the solid content is 40%;

[0059] The ammonium dihydrogen phosphate is of analytical purity;

[0060] The pretreated high-molecular water-absorbing resin is obtained by the following method: the high-molecular water-absorbing resin is pretreated by being soaked in a 2.5 mol / L ammonium dihydrogen phosphate solution at 25°C for 10 min, with a solid-liquid ratio of 1:100; the high-molecular water-absorbing resin has a particle size of 400 mesh, a water absorption rate of 500 times in pure water, and a liquid absorption rate of 8.6 times in the 2.5 mol / L ammonium dihydrogen phosphate solution.

[0061] Examples 1-6 and Comparative Examples 1-4

[0062] The preparation method of the magnesium phosphate-based cement grouting material provided in Examples 1-6 and Comparative Examples 1-4 comprises the following steps:

[0063] (1) Preparation of component A: a certain amount of calcined magnesium oxide, bentonite and hydroxypropyl methyl cellulose are weighed according to the mixing ratio in Tables 2 and 3, and stirred for 30 s until the raw materials are fully mixed; a certain amount of water reducing agent, defoaming agent and water are weighed according to the mixing ratio in Tables 2 and 3, and stirred for 30 s until fully mixed; the powder and liquid are mixed and stirred for 2 min to form component A.

[0064] (2) Preparation of component B: a certain amount of ammonium dihydrogen phosphate, sodium polyacrylate and pretreated high-molecular water-absorbing resin (in Comparative Example 2, the high-molecular water-absorbing resin is used) are weighed according to the mixing ratio in Tables 2 and 3, and stirred for 1 min until fully mixed to form component B.

[0065] Comparative Example 5 (cement-sodium silicate system)

[0066] The preparation method of the cement-sodium silicate dual-liquid grouting material comprises the following steps:

[0067] (1) Preparation of component A: a certain amount of cement is weighed according to the mixing ratio in Table 4, and a certain amount of polycarboxylic acid water reducing agent, silicone defoaming agent and water are weighed according to the mixing ratio in Table 4, and stirred for 30 s until fully mixed; the powder and liquid are mixed and stirred for 2 min to form component A.

[0068] (2) Preparation of component B: a certain amount of sodium silicate (40°Bé Baume) and water are weighed according to the mixing ratio in Table 4, and stirred for 2 min to form component B.

[0069] Table 2 Formulation of grouting material used in Examples 1-6 and Comparative Examples 1-4 (parts by weight)

[0070]

[0071] Table 3 Formulation of calcined magnesium oxide used in Examples 1-6 and Comparative Examples 1-4 (parts by weight)

[0072]

[0073] Among them, examples 1-5 verify the influence of the ratio of calcined magnesium oxide on the new phosphorus magnesium-based cement grouting plugging material; examples 6 and comparative examples 1-4 respectively verify the influence of bentonite, high molecular water-absorbing resin and sodium polyacrylate on the new phosphorus magnesium-based cement grouting plugging material.

[0074] Table 4 grouting material formula used in comparative example 5 (parts by weight)

[0075]

[0076] Performance test

[0077] Mix the A component and the B component of the above grouting material uniformly, inject into a 40*40*160 mm mold in two modes of air forming and underwater forming, demold after 0.5 h, and respectively perform curing in air and in water. Among them, the curing system in air is 20±2 ℃, relative humidity≥95%, and the curing system in water is 20±2 ℃; measure the compressive strength and calculate the water-land strength ratio after 28 days.

[0078] The underwater stone rate HR is the ratio of the volume of the underwater formed stone body to the initial volume of the slurry. Take 100 ml of freshly mixed grouting slurry and inject into a container containing 100 ml of water with a syringe, measure the volume of water and unstone slurry after 3 h. The stone rate HR calculation formula of the sample is:

[0079] HR=(V 浆 +V 水 -V0) / V 浆 ×100%(1)

[0080] V 浆 —The volume of the freshly mixed grouting slurry, take 100 ml;

[0081] V 水 —The volume of the injected water, take 100 ml;

[0082] V0—The volume of the remaining water and unstone slurry after 3 h.

[0083] The slurry anti-scouring retention rate is tested by the slurry anti-scouring performance test device built by the laboratory. The water tank is 200 cm long, 15 cm wide and 5 cm high. The water flow rate is controlled to be 0.4 m / s by adjusting the inlet valve. Each time 500 g of slurry is injected, recorded as M0, directly poured onto the detection plate 20 cm away from the water inlet to simulate the grouting process, and the injection process is kept uniform. When clear water continuously flows out at the outlet, measure the remaining slurry mass on the detection plate, recorded as M1, and calculate the slurry retention rate, i.e. GRR (grout retention ratio). The calculation formula of the slurry anti-scouring retention rate is:

[0084] GRR = M1 / M0 x 100% (2)

[0085] The test results are shown in Table 5.

[0086] Table 5 Performance test results of Examples 1-6 and Comparative Examples 1-5

[0087]

[0088] As can be seen from Table 5, compared with Comparative Example 5, the magnesium phosphate-based cement grouting materials prepared in Examples 1-6 all have lower setting time, higher 3h underwater stone formation rate, higher 28d underwater compressive strength, 28d water-land strength ratio and comparable or even higher resistance to dynamic water scouring, which indicates that the magnesium phosphate-based cement grouting material of the present application has the advantages of low shrinkage, short and adjustable setting time, high compressive strength, simple construction, low cost, green environmental protection, good slurry injection, high impermeability, good water dispersion resistance and good durability in long-term water soaking environment.

[0089] Examples 1-5 mainly verify the influence of calcined magnesium oxide on the new phosphorus-magnesium-based cement grouting and plugging material. As can be seen from Examples 1-5, with the increase of the light-heavy ratio, the setting time gradually decreases and the 3h underwater stone formation rate gradually increases, but the 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring all show a trend of first increasing and then decreasing.

[0090] Compared with Example 3, no bentonite is added in Example 6, and its 3h underwater stone formation rate, 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring all decrease, but are still significantly better than the existing cement-silicate system.

[0091] Compared with Example 3, no pretreated high molecular water-absorbing resin is added in Comparative Example 1, and its 3h underwater stone formation rate, 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring all decrease, but are still significantly better than the existing cement-silicate system.

[0092] Compared with Example 3, in Comparative Example 2, the pretreated high molecular water-absorbing resin is replaced by high molecular water-absorbing resin, and the content of dihydrogen phosphate is increased. The dihydrogen phosphate in the system directly reacts with magnesium oxide, the setting time is shortened, the reaction rate is too fast, the sample cracks, and its 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring significantly decrease.

[0093] Compared with Example 3, no sodium polyacrylate is added in Comparative Example 3, and its 3h underwater stone formation rate, 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring all significantly decrease, and its water-land strength ratio and resistance to dynamic water scouring are even lower than the existing cement-silicate system.

[0094] Compared with Example 3, no bentonite, SAP and sodium polyacrylate are added in Comparative Example 4, although the setting time is reduced, the 3h underwater stone rate, 28d underwater compressive strength, 28d water-land strength ratio and resistance to dynamic water scouring are significantly reduced, and the water-land strength ratio and resistance to dynamic water scouring are even lower than the existing cement-silicate system.

[0095] Compared with the prior art, the beneficial effects of the present application mainly include:

[0096] (1) high early strength, good late strength development, short and adjustable setting time, excellent water dispersion resistance, fast crack repair and strong adhesion.

[0097] (2) good raw material stability, convenient storage, green and environmentally friendly, and simple construction process.

[0098] (3) different calcined magnesium oxides are used in combination, so that magnesium oxides with different calcination temperatures react in stages in the early stage (within a few minutes), which can not only participate in the reaction to generate hydration products to provide initial strength as quickly as possible, but also prevent the initial reaction from being too intense to cause a large amount of heat release and cracking of the grouting material matrix.

[0099] (4) bentonite and light-burned magnesium oxide provide relatively high water absorption and swelling properties of magnesium phosphate cement; pretreated SAP can reduce the reaction rate and improve the water resistance and water dispersion resistance of the material. Water absorption can make the grouting process absorb part of the water in the crack, reducing the difficulty of grouting and achieving better grouting results; swelling can make the 3h underwater stone rate of the material reach more than 100%, preventing shrinkage from causing cracks.

[0100] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made in accordance with the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A magnesium phosphate-based cement grouting material, characterized in that, Its raw materials include component A and component B; wherein, by weight, component A comprises: 140-200 parts calcined magnesium oxide, 0-30 parts bentonite, 0.2-0.5 parts hydroxypropyl methylcellulose, 1-10 parts additives, and 70-140 parts water; component B comprises: 70-100 parts dihydrogen phosphate monophosphate, 20-50 parts pretreated superabsorbent polymer, 0.5-2 parts sodium polyacrylate, and 30-70 parts water; the calcined magnesium oxide is composed of lightly calcined magnesium oxide and heavy... The calcined magnesium oxide is compounded in a mass ratio of (2-4):1; the additives include at least one of defoamer and water-reducing agent; the pretreated superabsorbent polymer is obtained by soaking the superabsorbent polymer in an aqueous solution of dihydrogen phosphate; the first dihydrogen phosphate and the second dihydrogen phosphate are at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate; the molar ratio of magnesium to phosphorus in the calcined magnesium oxide and the first dihydrogen phosphate is (5.5-6.5):

1.

2. The magnesium phosphate-based cement grouting material according to claim 1, characterized in that, The calcination temperature of the lightly calcined magnesium oxide is 900-1000℃; The calcination temperature of the reheated magnesium oxide is 1600-1700℃.

3. The magnesium phosphate-based cement grouting material according to claim 1, characterized in that, The mass ratio of the lightly calcined magnesium oxide to the heavily calcined magnesium oxide is 3:

1.

4. The magnesium phosphate-based cement grouting material according to claim 1, characterized in that, The superabsorbent polymer has a particle size of 200-500 mesh, an absorption rate of 100-1000 times in pure water, and an absorption rate of 1-50 times in a 2.5 mol / L dihydrogen phosphate solution; and / or, The concentration of the aqueous solution of the second dihydrogen phosphate is 1-5 mol / L; and / or, The solid-liquid ratio of the superabsorbent polymer to the aqueous solution of the second dihydrogen phosphate is 1:(50-500); and / or, The soaking temperature is 20-30℃, and the soaking time is 10-60 minutes.

5. The magnesium phosphate-based cement grouting material according to claim 1, characterized in that, The bentonite has a particle size of 100-300 mesh; and / or, The viscosity of the hydroxypropyl methylcellulose is 100,000-300,000 mPa·s.

6. The magnesium phosphate-based cement grouting material according to claim 1, characterized in that, The magnesium phosphate-based cement grouting material, by weight, comprises the following components: Component A: 170-190 parts calcined magnesium oxide, 15-20 parts bentonite, 0.3-0.4 parts hydroxypropyl methylcellulose, 3-6 parts admixture, and 100-120 parts water; Component B: 80-90 parts dihydrogen phosphate monophosphate, 30-40 parts pretreated superabsorbent polymer, 0.8-1.2 parts sodium polyacrylate, and 40-60 parts water.

7. A method for preparing a magnesium phosphate-based cement grouting material as described in any one of claims 1-6, characterized in that, Includes the following steps: Calcined magnesium oxide, bentonite, and hydroxypropyl methylcellulose are mixed evenly to obtain a mixed powder; an additive and water are mixed evenly to obtain a mixed liquid; the mixed powder and the mixed liquid are mixed evenly to obtain component A; The first dihydrogen phosphate, sodium polyacrylate, pretreated superabsorbent polymer and water are mixed evenly to obtain component B.

8. The application of a magnesium phosphate-based cement grouting material as described in any one of claims 1-6, characterized in that, The magnesium phosphate-based cement grouting material is used for sealing leaking cracks.

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