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

Abstract

The application provides a magnesium phosphate cement-based grouting repair material and a preparation method thereof, and raw materials of the magnesium phosphate cement-based grouting repair material include: magnesium phosphate cement, fine aggregate and a composite reinforcing component; the composite reinforcing component includes: aluminum tripolyphosphate or an aluminum tripolyphosphate modified product and carboxymethyl chitosan. The application has high hourly strength and super-high later strength, and meets the repair and grouting requirements of high early strength and super-high strength concrete; meanwhile, the preparation method is simple and has strong operability.

Description

TECHNICAL FIELD

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

[0002] Cement-based pouring and grouting materials have good fluidity, micro-expansion, convenient construction, no pollution to the environment, good aging resistance and durability, and are widely used in reinforced concrete structure reinforcement and reconstruction, old concrete structure crack treatment, equipment foundation anchoring and fixing engineering, etc.

[0003] With the vigorous promotion of prefabricated buildings in China, the steel grouting sleeve wet connection technology used for connecting prefabricated concrete members requires grouting material to have super early strength, high fluidity and micro-expansion, etc. In prestressed post-tensioning members, the anchoring of prestressed members also requires the use of high early strength and high adhesion grouting material. The repair of airport runways has been difficult to adapt to economic development after 24 hours of traffic opening, and the application of super early strength cement-based grouting material can shorten the time of traffic opening. In emergency situations, the 2-hour compressive strength is required to be not less than 20 MPa.

[0004] High-strength concrete, as an energy-saving, environment-friendly and green building material, has been widely used in high-rise building structures, long-span bridge structures and some special structures due to its high compressive strength, strong anti-deformation ability, high density and low porosity. However, with the extension of service life, some defects have appeared, and high-strength and high-performance repair materials need to be developed.

[0005] In the prior art, cement-based grouting repair materials using magnesium phosphate cement as an adhesive have the characteristics of convenient construction, fast hardening, high early strength, micro-expansion, strong adhesion to the base material and good compatibility, and have more advantages than cement-based grouting repair materials prepared from Portland cement and sulphoaluminate cement. However, magnesium phosphate cement-based grouting repair materials have the defects of too fast setting at room temperature or higher temperature environment and large loss of fluidity, which limits their application range. Moreover, the early and late strength of such grouting repair materials after excessive retarding does not meet the requirements of super early strength and super high strength, and cannot meet the repair requirements of high-strength concrete.

[0006] The magnesium phosphate cement grouting material in Chinese patent CN 102643073A has the characteristics of good volume stability, fast early hardening, high strength, hydration at negative temperature, good corrosion resistance, and convenient construction. However, due to the limited retarding effect of borax, the grouting material has too fast hydration reaction speed and large loss of fluidity, and has limited application range due to insufficient construction time at normal environmental temperature.

[0007] The boric acid is used as a retarder in the magnesium phosphate grouting material for quick repair in Chinese patent CN108069692A, and the setting time is moderately controllable, but the hydration activity of the acid-base components is inhibited due to a large amount of boric acid, resulting in low early flexural and compressive strengths (1d, 5.3-8.2MPa, 37.1-51.1MPa), and limited late strength development, which cannot meet the engineering requirements of ultra-early strength and ultra-high strength.

[0008] A sleeve grouting material for negative temperature steel connection and a preparation method thereof are provided in Chinese patent CN111875338A, in which magnesium phosphate cement and sulphoaluminate cement are used as the main adhesive, borax is used as the main retarder, and lithium hydroxide and sodium sulfate are used as early strength agents, so that the grouting material can be constructed in a negative temperature environment, and has high 1d and 28d strengths, but the material components are too many, the preparation process is complex, and the setting time and 0.5h flow loss in a high temperature environment are not provided.

[0009] Therefore, the existing magnesium phosphate cement-based pouring and grouting repair material products still need to be further improved. SUMMARY

[0010] In view of the above prior art, the present application provides a grouting repair material based on magnesium phosphate cement and a preparation method thereof.

[0011] The grouting repair material based on magnesium phosphate cement and the preparation method thereof provided by the present application have the following advantages.

[0012] Preferably, the raw materials include 40-50 parts by mass of magnesium phosphate cement, 40-50 parts by mass of fine aggregate, and 5-10 parts by mass of the composite reinforcing component.

[0013] Preferably, the magnesium phosphate cement is composed of an alkali component, an acid component and a retarder, and the mass ratio of the alkali component, the acid component and the retarder is 1:0.30-0.40:0.08-0.12.

[0014] Preferably, the alkali component includes 80-90% by mass of heavy-burned magnesia powder and 10-20% by mass of metakaolin.

[0015] Preferably, the heavy-burned magnesia powder is obtained by calcining and grinding magnesite at a high temperature of more than 1300°C, and has a MgO content of 88-92% and a fineness of 200-350 mesh; and the metakaolin is obtained by calcining and grinding at a high temperature of more than 800°C, and has a fineness of 1000-1500 mesh.

[0016] The re-burned magnesium oxide powder and the metakaolin of different fineness are proportioned to improve the particle size distribution of the alkali component powder, and further improve the pore structure of the hardened body of the magnesium phosphate cement-based material.

[0017] Preferably, the acid component comprises ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, wherein the mass ratio of the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate is 1:0.2-0.3; the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are both industrial grade, and the fineness of both is 60-150 mesh.

[0018] The ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are proportioned to generate the magnesium ammonium phosphate hydration product with high adhesion and stable performance by using the high reaction activation energy between the ammonium dihydrogen phosphate and the re-burned magnesium oxide, and to control the hydration heat release speed and the initial hydration speed by using the crystal phase transformation of the disodium hydrogen phosphate dodecahydrate to absorb heat.

[0019] Preferably, the retarder is boric acid or borax, and the boric acid or borax is industrial grade, and the fineness is 60-150 mesh.

[0020] The boric acid or borax can adjust the setting time and hydration speed of the freshly mixed magnesium phosphate cement slurry by generating a boric acid salt protective film, dissolving heat absorption cooling and adjusting pH value, but can inhibit the later reaction activity of the magnesium phosphate cement-based material slurry.

[0021] Preferably, the fine aggregate is quartz sand, and the particle size of the quartz sand is 0.5-2.0 mm.

[0022] Preferably, the mass ratio of the aluminum tripolyphosphate or aluminum tripolyphosphate modified product and the carboxymethyl chitosan is 1:0.4-0.6; the aluminum tripolyphosphate or aluminum tripolyphosphate modified product is superior grade, and the fineness is 800-1250 mesh; the carboxymethyl chitosan is food grade, the degree of carboxylation is greater than 80%, and the fineness is 800-1250 mesh.

[0023] The addition of the appropriate amount of aluminum tripolyphosphate can stimulate the later hydration activity of the magnesium phosphate cement slurry, so that the later strength of the hardened body is improved; the addition of the appropriate amount of carboxymethyl chitosan can fill the pores of the magnesium phosphate cement-based slurry by using the film forming effect and the adsorption effect, so that the compactness of the hardened body is improved, and the early and later strengths of the hardened body are further improved.

[0024] The application also provides a preparation method of the magnesium phosphate cement-based grouting repair material.

[0025] S1, re-burned magnesium oxide powder, metakaolin, disodium hydrogen phosphate dodecahydrate, boric acid or borax, and quartz sand are stirred and mixed for 2-3 min as A component, and ammonium dihydrogen phosphate, aluminum tripolyphosphate or aluminum tripolyphosphate modified product, and carboxymethyl chitosan are stirred and mixed for 2-3 min as B component;

[0026] S2, under the natural environment condition of 5℃-30℃, 40%-70% RH, the A component and the B component are mixed with an appropriate amount of water and stirred for 4-5 min to prepare the grouting repair material.

[0027] Compared with the prior art, the grouting repair material and the preparation method thereof have the following beneficial effects: the grouting repair material slurry can be applied under the condition of 5℃-30℃, the setting time and the initial fluidity and the 0.5h fluidity all meet the requirements of self-compacting and grouting materials, and the grouting repair material has high hourly strength and ultrahigh later strength, meeting the requirements of high early strength and ultrahigh strength concrete repair and grouting; and the preparation method is simple and has strong operability. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a hydration temperature curve comparison diagram of the grouting repair material obtained in Example 1 of the present application and the grouting repair materials obtained in Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the present application is further described below in combination with specific drawings.

[0030] Example 1

[0031] A grouting repair material based on magnesium phosphate cement, the raw materials of which include, by mass fraction: magnesium phosphate cement 44 parts, fine aggregate 50 parts, and composite reinforcing component 6 parts.

[0032] The magnesium phosphate cement is composed of an alkali component, an acid component and a retarder, and the mass ratio of the alkali component, the acid component and the retarder is 1:0.33:0.08.

[0033] The alkali component includes, by mass fraction: heavy-burned magnesia powder 80%, and metakaolin 20%. The heavy-burned magnesia powder is obtained by calcining and pulverizing magnesite at a high temperature of more than 1300℃, and has a MgO content of 90% and a fineness of 200 mesh; the metakaolin is obtained by calcining and pulverizing at a high temperature of more than 800℃, and has a fineness of 1000 mesh.

[0034] The acid component includes ammonium dihydrogen phosphate and dodecahydrate disodium hydrogen phosphate, and the mass ratio of the ammonium dihydrogen phosphate and the dodecahydrate disodium hydrogen phosphate is 1:0.21; both the ammonium dihydrogen phosphate and the dodecahydrate disodium hydrogen phosphate are industrial grade, and both have a fineness of 60 mesh.

[0035] The retarder is borax, and the borax is industrial grade and has a fineness of 60 mesh.

[0036] Further, the fine aggregate is quartz sand, and the particle size of the quartz sand can be 1.0-2.0 mm.

[0037] Further, the composite reinforcing component comprises: aluminum tripolyphosphate, carboxymethyl chitosan. The mass ratio of the aluminum tripolyphosphate and the carboxymethyl chitosan is 1:0.6.

[0038] The aluminum tripolyphosphate is of an excellent grade, and the fineness is 1000 mesh.

[0039] The carboxymethyl chitosan is of a food grade, the degree of carboxylation is greater than 80%, and the fineness is 1000 mesh.

[0040] Further, the preparation method of the grouting repair material based on the magnesium phosphate cement comprises the following steps:

[0041] S1, using a dry powder mixer to mix and stir heavy burned magnesia powder, metakaolin, disodium hydrogen phosphate dodecahydrate, borax, and quartz sand for 2.5 min as A component, using a dry powder mixer to mix and stir ammonium dihydrogen phosphate, aluminum tripolyphosphate, and carboxymethyl chitosan for 2.5 min as B component;

[0042] S2, mixing and stirring the dry powders of the A component and the B component with an appropriate amount of water (according to the initial fluidity of the slurry body reaching the specified requirements) for 4.5 min under the natural environmental conditions of 20℃ and 55% RH to prepare the grouting repair material.

[0043] Example 2

[0044] A grouting repair material based on the magnesium phosphate cement, the raw materials of which include, by mass fraction: magnesium phosphate cement 40 parts, fine aggregate 55 parts, and composite reinforcing component 5 parts.

[0045] The magnesium phosphate cement is composed of an alkali component, an acid component, and a retarder, and the mass ratio of the alkali component, the acid component, and the retarder is 1:0.40:0.10.

[0046] The alkali component includes, by mass percentage: heavy burned magnesia powder 90%, and metakaolin 10%. The heavy burned magnesia powder is obtained by calcining and grinding magnesite at a high temperature of more than 1300℃, wherein the MgO content is 90%, and the fineness is 350 mesh; the metakaolin is obtained by calcining and grinding at a high temperature of more than 800℃, and the fineness is 1250 mesh.

[0047] The acid component includes ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, and the mass ratio of the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate is 1:0.26; both the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are of an industrial grade, and the fineness of both is 120 mesh.

[0048] The retarder is borax, the borax is industrial grade, and the fineness is 120 mesh.

[0049] Further, the fine aggregate is quartz sand, and the particle size of the quartz sand can be 0.5-2.0 mm.

[0050] Further, the composite reinforcing component includes aluminum tripolyphosphate and carboxymethyl chitosan, and the mass ratio of the aluminum tripolyphosphate to the carboxymethyl chitosan is 1:0.4.

[0051] The aluminum tripolyphosphate is of superior grade, and the fineness is 1000 mesh.

[0052] The carboxymethyl chitosan is of food grade, the degree of carboxylation is greater than 80%, and the fineness is 1000 mesh.

[0053] Further, the preparation method of the grouting repair material based on magnesium phosphate cement includes the following steps:

[0054] S1, using a dry powder mixer to mix and stir heavy burned magnesia powder, metakaolin, disodium hydrogen phosphate dodecahydrate, borax, and quartz sand for 2 minutes as A component, using a dry powder mixer to mix and stir ammonium dihydrogen phosphate, aluminum tripolyphosphate, and carboxymethyl chitosan for 3 minutes as B component;

[0055] S2, mixing and stirring the dry powders of the A component and the B component with an appropriate amount of water (according to the initial fluidity of the slurry body reaching the specified requirements) for 5 minutes under the natural environmental conditions of 5°C and 70% RH to prepare the grouting repair material.

[0056] Example 3

[0057] A grouting repair material based on magnesium phosphate cement, the raw materials of which include, by mass fraction, 42 parts of magnesium phosphate cement, 52 parts of fine aggregate, and 6 parts of composite reinforcing component.

[0058] The magnesium phosphate cement is composed of an alkali component, an acid component, and a retarder, and the mass ratio of the alkali component, the acid component, and the retarder is 1:0.36:0.10.

[0059] The alkali component includes, by mass percentage, 85% of heavy burned magnesia powder and 15% of metakaolin. The heavy burned magnesia powder is obtained by calcining and pulverizing magnesite at a temperature of more than 1300°C, and the MgO content is 90% and the fineness is 280 mesh. The metakaolin is obtained by calcining and pulverizing at a temperature of more than 800°C, and the fineness is 1000 mesh.

[0060] The acid component includes ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, and the mass ratio of the ammonium dihydrogen phosphate to the disodium hydrogen phosphate dodecahydrate is 1:0.24. Both the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are of industrial grade, and the fineness of both is 100 mesh.

[0061] The retarder is boric acid, the boric acid has a fineness of 100 mesh.

[0062] Further, the fine aggregate is quartz sand, and the particle size of the quartz sand can be 0.5-2.0 mm.

[0063] Further, the composite reinforcing component includes: aluminum tripolyphosphate, carboxymethyl chitosan. The mass ratio of the aluminum tripolyphosphate to the carboxymethyl chitosan is 1:0.5.

[0064] The aluminum tripolyphosphate is of an excellent grade and has a fineness of 1000 mesh.

[0065] The carboxymethyl chitosan is of a food grade, has a degree of carboxylation greater than 80%, and has a fineness of 1000 mesh.

[0066] Further, the preparation method of the grouting repair material based on magnesium phosphate cement includes the following steps:

[0067] S1, using a dry powder mixer to mix and stir heavy burned magnesia powder, metakaolin, dodecahydrate sodium phosphate dibasic, boric acid, and quartz sand for 3 min as A component, using a dry powder mixer to mix and stir ammonium dihydrogen phosphate, aluminum tripolyphosphate, and carboxymethyl chitosan for 2 min as B component;

[0068] S2, mixing and stirring the dry powders of the A component and the B component with an appropriate amount of water (according to the initial fluidity of the slurry body reaching the specified requirements) for 4 min under the natural environmental conditions of 30°C and 40% RH to prepare the grouting repair material.

[0069] Comparative Example 1

[0070] A grouting repair material based on magnesium phosphate cement, the raw materials of which include, by mass fraction: magnesium phosphate cement 50 parts, fine aggregate 50 parts.

[0071] The magnesium phosphate cement is composed of an alkali component, an acid component, and a retarder, and the mass ratio of the alkali component, the acid component, and the retarder is 1:0.33:0.08.

[0072] The alkali component includes, by mass percentage: heavy burned magnesia powder 80%, metakaolin 20%. The heavy burned magnesia powder is obtained by calcining and pulverizing magnesite at a high temperature of more than 1300°C, and has a MgO content of 90% and a fineness of 200 mesh; the metakaolin is obtained by calcining and pulverizing at a high temperature of more than 800°C, and has a fineness of 1000 mesh.

[0073] The acid component includes ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, wherein the mass ratio of the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate is 1:0.21; the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are both industrial grade, and the fineness is 60 mesh.

[0074] The retarder is borax, the borax is industrial grade, and the fineness is 60 mesh.

[0075] Further, the fine aggregate is quartz sand, and the particle size of the quartz sand can be 1.0-2.0 mm.

[0076] Further, the preparation method of the grouting repair material based on magnesium phosphate cement comprises the following steps:

[0077] S1, using a dry powder mixer to mix and stir heavy burned magnesia powder, metakaolin, disodium hydrogen phosphate dodecahydrate, borax, and quartz sand for 2.5 min as A component, and ammonium dihydrogen phosphate as B component;

[0078] S2, mixing and stirring the dry powder of the A component and the B component with an appropriate amount of water (according to the initial fluidity of the slurry body reaching the specified requirement) for 4.5 min under the natural environmental conditions of 20℃ and 55% RH to prepare a grouting repair material.

[0079] Comparative Example 2

[0080] A grouting repair material based on magnesium phosphate cement, according to mass parts, the raw materials thereof include: magnesium phosphate cement 44 parts, fine aggregate 50 parts, and aluminum tripolyphosphate (enhanced component) 6 parts.

[0081] The magnesium phosphate cement is composed of an alkali component, an acid component, and a retarder, and the mass ratio of the alkali component, the acid component, and the retarder is 1:0.33:0.08.

[0082] According to mass percentage, the alkali component includes: heavy burned magnesia powder 80%, and metakaolin 20%. The heavy burned magnesia powder is obtained by calcining and grinding magnesite at a high temperature above 1300℃, wherein the MgO content is 90%, and the fineness is 200 mesh; the metakaolin is obtained by calcining and grinding at a high temperature above 800℃, and the fineness is 1000 mesh.

[0083] The acid component is ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, wherein the mass ratio of the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate is 1:0.21; the ammonium dihydrogen phosphate and the disodium hydrogen phosphate dodecahydrate are both industrial grade, and the fineness is 60 mesh.

[0084] The retarder is borax, the borax is industrial grade, and the fineness is 60 mesh.

[0085] Further, the fine aggregate is quartz sand, and the particle size of the quartz sand can be 1.0-2.0 mm.

[0086] Further, the reinforcing component aluminum tripolyphosphate is of an excellent grade, and the fineness is 1000 mesh.

[0087] Further, the preparation method of the grouting repair material based on the magnesium phosphate cement comprises the following steps:

[0088] S1, using a dry powder mixer to mix and stir heavy burned magnesia powder, metakaolin, disodium hydrogen phosphate dodecahydrate, borax and quartz sand for 2.5 min as A component, using a dry powder mixer to mix and stir ammonium dihydrogen phosphate and aluminum tripolyphosphate for 2.5 min as B component;

[0089] S2, mixing and stirring the dry powders of the A component and the B component with an appropriate amount of water (according to the initial fluidity of the slurry body reaching the specified requirements) for 4.5 min under the natural environmental conditions of 20℃ and 55% RH to prepare the grouting repair material.

[0090] Test example

[0091] The grouting repair materials prepared in the above examples 1-3 and comparative examples 1-2 are respectively tested in terms of initial fluidity, 30 min fluidity, 3h flexural and compressive strength, 3d flexural and compressive strength, 28d flexural and compressive strength, 3h vertical expansion rate, difference between 24h and 3h vertical expansion rate and bleeding rate, and the obtained results are shown in Tables 1 and 2.

[0092] Table 1: Various properties of the grouting repair material

[0093]

[0094] As shown in Table 1, the initial fluidity of the grouting repair material prepared in the examples 1-3 of the present application is 310-320 mm; the 30 min fluidity is 270-280 mm; the 3h vertical expansion rate is 0.08-0.10%; the difference between 24h and 3h vertical expansion rate is 0.05-0.06%, and the bleeding rate is 0%. All the performance indicators are higher than the requirements of the industry standard JG / T408-2013.

[0095] Table 2: Mechanical properties and water absorption rate (28d) of the grouting repair material

[0096]

[0097]

[0098] The water absorption was determined according to JGJ / T70-2009 "Standard for Testing Methods of Basic Properties of Building Mortar", the test piece maintained to the specified age was dried at 60 ℃±3 ℃ for 48 h, and then the mass m0 was determined, then the test piece was immersed in water (20 ℃±3 ℃) with the forming surface facing downward, the immersion height was kept at 35 mm, and the bottom surface of the test piece could not contact the container, after 48 h, the surface water was wiped off with a wrung wet cloth, and then the mass m1 was determined, and the calculation formula of the water absorption was as follows:

[0099] W x =(m1-m0) / m0

[0100] As shown in Table 2, the 3h compressive strength of the grouting repair materials prepared in Examples 1-3 is 63.5-70.2 MPa, which has basically reached the strength (60.0-90.0 MPa) requirement of high-strength concrete. The 3d compressive strength is 89.6-101.5.7 MPa; the 28d compressive strength is 100.6-118.5 MPa, and the compressive strength is much higher than the requirement of the compressive strength at each age in the industry standard JG / T408-2013. And the 28d compressive strength has reached the strength (90.0-120.0 MPa) requirement of super-high-strength concrete.

[0101] The mixing ratio and aggregate ratio of the magnesium phosphate cement of Comparative Example 1 are the same as those of Example 1, and the difference is that the composite reinforcing component is not contained. As shown in Table 2, the strength of Example 1 and Comparative Example 1, the addition of the composite reinforcing agent can make the 3h and 28d flexural and compressive strength of the magnesium phosphate cement-based grouting repair material increase by more than 20%.

[0102] The mixing ratio and aggregate ratio of the magnesium phosphate cement of Comparative Example 2 are the same as those of Comparative Example 1 and Example 1, compared with Comparative Example 1, the difference is that aluminum tripolyphosphate is added as a reinforcing component, and compared with Example 1, the difference is that the reinforcing component is only aluminum tripolyphosphate. As shown in Table 2, the strength of Comparative Example 1 and Comparative Example 2, the single-doped aluminum tripolyphosphate reinforcing agent can make the 3h and 28d flexural and compressive strength of the magnesium phosphate cement-based grouting repair material increase by more than 10%. As shown in Table 2, the strength of Comparative Example 2 and Example 1, the double-doped carboxymethyl chitosan reinforcing agent can make the 3h flexural and compressive strength of the magnesium phosphate cement-based grouting repair material increase by more than 10%, and the 28d flexural and compressive strength increase by nearly 10%.

[0103] Figure 1 The hydration temperature curves of Comparative Example 1, Comparative Example 2 and Example 1 are shown in Figure 1. Figure 1It can be seen that the temperature of the system rapidly decreases due to the endothermic dissolution of the borax retarder and the complex phosphate of the acid component, and the minimum temperature is about 10℃ lower than the room temperature. Subsequently, the temperature of the slurry gradually increases, but the temperature of the slurry does not exceed 40℃ (initial setting temperature) within 30 minutes, indicating that the initial setting time of the slurry is greater than 30 minutes. Due to the inhibition of the acid-base reaction activity by the borax retarder, the maximum hydration temperature of the comparative example 1 is only 66.7℃, resulting in lower early and late strengths of the hardened grouting repair material (see Table 2). In the comparative example 2, the hydration activity of the slurry with only the addition of the aluminum tripolyphosphate strengthening component is excited, and the maximum hydration temperature of the slurry is increased to 89.6℃, which significantly improves the early and late strengths of the hardened grouting repair material (see Table 2). However, the addition of the aluminum tripolyphosphate increases the hydration speed and the initial setting time of the freshly mixed repair material slurry (see Table 1), resulting in a significant decrease in the 30-minute fluidity (see Table 1), which cannot meet the requirements of the grouting slurry. In the example 1, the aluminum tripolyphosphate and the carboxymethyl chitosan strengthening components are added together, the hydration activity of the repair material slurry is further excited, the maximum hydration temperature of the slurry is increased to 90.2℃, and the early and late strengths of the hardened repair material are improved compared with the comparative example 2 (see Table 2). The carboxymethyl chitosan also has a certain retarding effect, the hydration speed of the freshly mixed repair material slurry is slower than that of the comparative example 2 (see Table 1), the decrease in the 30-minute fluidity of the slurry is reduced (see Table 1), and the standard requirements of the grouting slurry can be met. Figure 1 Figure 1

[0104] In a 25℃±2℃ environment, the magnesium phosphate cement-based repair material slurry is prepared (the time is recorded from the time of adding water, and the temperature change of the slurry is recorded by a thermometer), 200g of the freshly mixed repair material slurry is loaded into a thermos cup, a K-type thermocouple is inserted in the middle, the process is completed within 2 minutes, and an automatic temperature recorder is used to record the temperature change of the hydration system (the data of the first 8 minutes is measured by a thermometer).

[0105] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure, direct or indirect application in other related technical fields, is also within the patent protection scope of the present application.​​

Claims

1. A grouting repair material based on magnesium phosphate cement, characterized in that, Its raw materials include: magnesium phosphate cement, fine aggregate, and composite reinforcing components; the composite reinforcing components include: aluminum tripolyphosphate or modified aluminum tripolyphosphate products, and carboxymethyl chitosan; the magnesium phosphate cement is composed of alkali components, acid components, and retarder, and the mass ratio of the alkali components, acid components, and retarder is 1:0.30-0.40:0.08-0.12; by mass percentage, the alkali components include: 80-90% calcined magnesium oxide powder and 10-20% metakaolin; the calcined magnesium oxide powder is obtained by calcining and grinding magnesite at a high temperature above 1300℃, wherein the MgO content is 88-92% and the fineness is 200-350 mesh; the metakaolin is obtained by calcining and grinding at a high temperature above 800℃, and the fineness is 1000-1500 mesh.

2. The grouting and repair material based on magnesium phosphate cement as described in claim 1, characterized in that, By weight, its raw materials include: 40-50 parts magnesium phosphate cement, 40-50 parts fine aggregate, and 5-10 parts composite reinforcing components.

3. The grouting and repair material based on magnesium phosphate cement as described in claim 1, characterized in that, The acid component includes ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate, wherein the mass ratio of ammonium dihydrogen phosphate to disodium hydrogen phosphate dodecahydrate is 1:0.2-0.3; both ammonium dihydrogen phosphate and disodium hydrogen phosphate dodecahydrate are industrial grade and have a fineness of 60-150 mesh.

4. The grouting and repair material based on magnesium phosphate cement as described in claim 1, characterized in that, The retarder is boric acid or borax, which is industrial grade with a fineness of 60-150 mesh.

5. The grouting repair material based on magnesium phosphate cement as described in claim 1 or 2, characterized in that, The fine aggregate is quartz sand, and the particle size of the quartz sand is 0.5-2.0 mm.

6. The grouting and repair material based on magnesium phosphate cement as described in claim 1 or 2, characterized in that, The mass ratio of aluminum tripolyphosphate or its modified form to carboxymethyl chitosan is 1:0.4-0.6; the aluminum tripolyphosphate or its modified form is of premium grade with a fineness of 800-1250 mesh; the carboxymethyl chitosan is of food grade with a carboxylation degree greater than 80% and a fineness of 800-1250 mesh.

7. A method for preparing a grouting repair material based on magnesium phosphate cement, characterized in that, Includes the following steps: S1. Mix calcined magnesium oxide powder, metakaolin, disodium hydrogen phosphate dodecahydrate, boric acid or borax, and quartz sand for 2-3 minutes as component A. Mix ammonium dihydrogen phosphate, aluminum tripolyphosphate or modified aluminum tripolyphosphate, and carboxymethyl chitosan for 2-3 minutes as component B. S2. Under natural environmental conditions of 5℃-30℃ and 40%-70%RH, the components A and B are mixed with an appropriate amount of water and stirred for 4-5 minutes to obtain the grouting repair material.

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