Negative temperature tunnel grouting material and preparation method thereof

Abstract

This invention discloses a negative temperature grouting material and its preparation method, belonging to the field of building materials technology. The material comprises the following components in parts by weight: 350-500 parts cementitious material, 500-650 parts heat source material, 3-7 parts water-reducing component, 0.5-3 parts expansion component, 100-140 parts antifreeze component, 1-3 parts retarding component, 10-20 parts rust-inhibiting component, and 0.2-0.8 parts stabilizing component. The preparation method of the heat source material is as follows: first, remove chloride ions from the salt mud; then, maintain the temperature at 350-500℃ for 2-6 hours, raise the temperature to 850-900℃ and maintain it for 2-6 hours, continue raising the temperature to 1100-1300℃ and maintain it for 3-6 hours, and cool to obtain a calcined product; add sodium tripolyphosphate and melamine to the calcined product, then grind and sieve to obtain powder; mix the powder with sulfoaluminate cement to obtain the final product. Under the combined action of the components, the grouting material of the present invention can maintain high fluidity even in negative temperature environments, and also has excellent mechanical properties. Both early strength and later strength can meet the requirements of practical applications.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a negative temperature grouting material and its preparation method. Background Technology

[0002] With the increasing maturity of prestressed concrete technology, prestressed concrete structures have been widely used in engineering projects. During the fabrication of prestressed concrete components, pre-drilled ducts are required for the prestressing steel bars to pass through. After prestressing is applied to the steel bars, grouting material is filled into the ducts to bond the prestressing steel bars with the structural concrete, achieving excellent mechanical and structural properties. Duct grouting, as a crucial step in the construction process of post-tensioned prestressed structures, is receiving increasing attention. Quality problems in duct grouting can severely impact the safety, durability, and reliability of prestressed concrete structures. Therefore, the performance of the grouting material used in the duct grouting process is paramount to ensuring the safety and durability of post-tensioned prestressed concrete structures. High-performance grouting materials not only provide fluidity conducive to grouting but also possess reliable stability to maintain the homogeneity of the grout before setting. They should also exhibit a certain degree of micro-expansion to facilitate fuller filling of the ducts, and the hardened grouting material should possess strength no less than that of the beam concrete. Good fluidity facilitates the smooth flow of grout within the pipe, filling narrow and tortuous passages; good stability ensures the uniformity of the grout, preventing segregation and bleeding under pressure; micro-expansion allows the grout to fill the pipe more fully, avoiding shrinkage before setting, and the later-stage micro-expansion can compensate for later-stage volume shrinkage.

[0003] Grouting materials for prestressed concrete ducts are mainly composed of cement paste, water-reducing agents, expanding agents, mineral admixtures, and other materials. They are commonly used in post-tensioned prestressed concrete duct grouting projects, serving three main purposes: first, protecting prestressing tendons from corrosion and ensuring the safety of the prestressed structure; second, ensuring the bond between the prestressing tendons and concrete, allowing for effective prestress transfer and enabling the tendons and concrete to work together; and third, eliminating fatigue damage to anchorages caused by stress changes under repeated loading, extending anchorage service life, and improving structural reliability. However, current post-tensioned prestressed concrete duct grouting materials generally suffer from the following problems: ① They cannot be applied normally below 5℃, making them unsuitable for winter construction conditions in northern regions; ② The grout has poor fluidity and suffers significant losses at sub-zero temperatures; ③ The grout has a long setting time and slow strength gain at sub-zero temperatures; ④ The grout is not dense after hardening at sub-zero temperatures and exhibits frost heave. These defects seriously affect the durability and design service life of the beam structure.

[0004] Therefore, there is an urgent need to develop a grouting material with high fluidity and high strength even in low-temperature environments, so as to realize the construction of prestressed concrete grouting in frigid regions during winter. Summary of the Invention

[0005] In view of the shortcomings of the prior art, one of the objectives of this invention is to provide a negative temperature grouting material and its preparation method. This grouting material can maintain high fluidity even in negative temperature environments (-15℃ to -5℃), and also has excellent mechanical properties. Its early strength and later strength can meet the requirements of practical applications. It can solve the problems of poor fluidity, long setting time and low strength of existing grouting materials in negative temperature environments.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] A negative temperature grouting material comprises the following components in parts by weight: 350-500 parts of cementitious material, 500-650 parts of heat source material, 3-7 parts of water-reducing component, 0.5-3 parts of expansion component, 100-140 parts of antifreeze component, 1-3 parts of retarding component, 10-20 parts of rust-inhibiting component, and 0.2-0.8 parts of stabilizing component;

[0008] The method for preparing the heat source material includes the following steps:

[0009] S1. Remove chloride ions from the salt mud to obtain filter residue;

[0010] S2. Dry the filter residue, then keep it at 350-500℃ for 2-6 hours, raise the temperature to 850-900℃ and keep it at 2-6 hours, continue to raise the temperature to 1100-1300℃ and keep it at 3-6 hours, and then cool to obtain the calcined product.

[0011] S3. Sodium tripolyphosphate and melamine are added to the calcination product of step S2, and then the product is ground and sieved to obtain powder.

[0012] S4. Mix the powder from step S3 with sulfoaluminate cement to obtain the heat source material.

[0013] In the negative-temperature grouting material of this invention, the heat source material can provide heat in stages, enabling the cementitious material to have sufficient heat of hydration under negative temperature conditions, thus ensuring the normal hydration of the cementitious material in the grouting material throughout the process. Furthermore, the heat source material can also improve the fluidity of the grouting material. This invention provides heat in stages through the heat source material; improves the fluidity of the grouting material through water-reducing components; ensures that the mixing water does not freeze under negative temperature conditions through antifreeze components, allowing the cementitious material of the grouting material to continue hydrating; prevents corrosion of prestressing tendons used in conjunction with the grouting material through rust-inhibiting components; prevents bleeding after mixing of the grouting material through stabilizing components, thus stabilizing the quality; regulates the initial and final setting times of the grouting material through retarding components, giving it both longer operability and a suitable final setting time, thereby ensuring early strength development; and maintains the early expansion properties of the grouting material through expansion components. Under the combined action of the components, the grouting material of the present invention can maintain high fluidity even in negative temperature environments, and also has excellent mechanical properties. Both early strength and later strength can meet the requirements of practical applications.

[0014] The specific principle of the heat source material of this invention providing heat in stages is as follows:

[0015] Sulfoaluminate cement in the heat source material provides an early heat source. Sulfoaluminate cement has the characteristics of rapid reaction and high heat release under negative temperature environments. It first reacts with water, releasing a large amount of heat of hydration. The hydration products (ettringite and alumina gel) enhance the early strength of the grouting material. More importantly, the heat released during hydration raises the temperature of the entire grout. Due to the increased temperature, tricalcium aluminate in silicate cement also begins to react, rapidly releasing a large amount of heat of hydration. While continuing to raise the system temperature, the ettringite formed in conjunction with it further enhances the early strength (1-3 days) of the grouting material.

[0016] Step S2 yields calcined products mainly consisting of silica, calcium oxide, and magnesium oxide. After grinding in step S3, sodium tripolyphosphate is embedded in the internal pores of calcium oxide and magnesium oxide, and further coated on their surfaces. This surface-coated sodium tripolyphosphate prevents calcium oxide from reacting prematurely, ensuring it reacts with water in the middle stage to generate calcium hydroxide, releasing a large amount of heat and providing a heat source to sustain the middle-stage hydration process of silicate cement. Simultaneously, the generated calcium hydroxide provides alkalinity to the system, allowing the mineral powder in the cementitious material to undergo a "secondary hydration" reaction under alkaline conditions, thus improving the mechanical properties of the grouting material.

[0017] The magnesium oxide prepared by the method of this invention has low activity, and the sodium tripolyphosphate coating on the surface can further delay the hydration of magnesium oxide, so that magnesium oxide reacts with water in the later stage, releasing heat to provide a heat source for the later stage and maintaining the later hydration process of silicate cement.

[0018] Preferably, in step S3, the mass of sodium tripolyphosphate is 0.1% to 0.5% of the calcined product, and the mass of melamine is 0.5% to 1% of the calcined product.

[0019] Preferably, in step S3, the powder is ground until the residue on an 80μm square-hole sieve is less than 20%.

[0020] Preferably, in step S4, the mass ratio of the powder to the sulfoaluminate cement is (2-6):1.

[0021] More preferably, the mass fraction of NaCl in the salt mud is less than 2.5%. The specific operation for removing chloride ions from the salt mud in step S1 is as follows: soak the salt mud in water, filter it, and take the filter residue. Repeat the above operation until the filtrate is titrated with silver nitrate solution and no precipitate is produced.

[0022] Preferably, the cementing material includes silicate cement, mineral powder, and silica fume.

[0023] Preferably, the water-reducing components include a polycarboxylate water-reducing agent and a naphthalene-based water-reducing agent in a mass ratio of (3-7):1.

[0024] Preferably, the retarding component includes citric acid and sodium gluconate; the rust-inhibiting component includes at least one of calcium nitrite, sodium benzoate, ammonium heptamolybdate, sodium molybdate, and sodium hexametaphosphate; and the stabilizing component is cellulose ether or starch ether.

[0025] Preferably, the expanding component is azodicarbonamide; the antifreeze component is ethylene glycol.

[0026] Another objective of this invention is to provide a method for preparing negative temperature grouting material, comprising the following steps: weighing the cementitious material, heat source material, water-reducing component, expansion component, antifreeze component, retarding component, rust-inhibiting component and stabilizing component by weight and mixing them evenly, then adding water accounting for 26% to 28% of the total mass of the cementitious material and heat source material and stirring evenly to obtain the final product.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] (1) In the negative temperature grouting material of the present invention, the heat source material can provide heat in stages, so that the cementitious material has sufficient heat of hydration under negative temperature conditions to ensure the normal hydration of the cementitious material in the grouting material throughout the process. In addition, the heat source material can also improve the fluidity of the grouting material. The present invention provides heat in stages through the heat source material; improves the fluidity of the grouting material through the water-reducing component; ensures that the mixing water does not freeze under negative temperature conditions through the antifreeze component, so that the cementitious material of the grouting material continues to hydrate; prevents the prestressing tendons used in conjunction with the grouting material from rusting through the rust-inhibiting component; prevents the bleeding of the grouting material after mixing through the stabilizing component, so as to stabilize the quality; regulates the initial setting time and final setting time of the grouting material through the retarding component, so that it has both long operability and a suitable final setting time, thereby ensuring the development of early strength; and maintains the early expansion of the grouting material through the expansion component. Under the combined action of the components, the grouting material of the present invention can maintain high fluidity even in negative temperature environments, and also has excellent mechanical properties. Both early strength and later strength can meet the requirements of practical applications.

[0029] (2) This invention uses salt mud as the main raw material to prepare negative temperature grouting material for pore channels. Salt mud is applied on a large scale to pore grouting material. The utilization rate of salt mud is high, and waste salt mud can be rationally utilized. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following examples and comparative examples, the main components of the salt mud are as follows: SiO2 mass fraction of 50.43%, water mass fraction of approximately 36%, CaCO3 mass fraction of approximately 8.14%, Mg(OH)2 mass fraction of 4.34%, NaCl mass fraction of approximately 1.09%, and a small amount of Fe2O3. In the cementitious material, the silicate cement strength grade is not lower than 52.5, the mineral powder technical grade is S95 or higher, the silica fume 7-day activity index is not lower than 110%, and the mass ratio of silicate cement:mineral powder:silica fume is (30-40):(2-5):1.

[0032] Unless otherwise specified in the following embodiments and comparative examples, the preparation method of the negative temperature grouting material of the present invention is as follows: weigh the cementitious material, heat source material, water-reducing component, expansion component, antifreeze component, retarding component, rust-inhibiting component and stabilizing component according to the weight parts, dry mix them evenly, and then add water accounting for 26% to 28% of the total mass of cementitious material and heat source material and stir evenly to obtain the final product.

[0033] Example 1

[0034] This embodiment provides a negative temperature grouting material for ducts, the raw materials of which include the following components in parts by weight: 425 parts of cementitious material, 575 parts of heat source material, 5 parts of water-reducing component, 2 parts of expansion component, 120 parts of antifreeze component, 2 parts of retarding component, 15 parts of rust-inhibiting component, 0.5 parts of stabilizing component, and 270 parts of water.

[0035] The cementitious material is composed of silicate cement, mineral powder, and silica fume mixed in a mass ratio of 30:2:1; the water-reducing component is composed of polycarboxylate superplasticizer and naphthalene-based superplasticizer mixed in a mass ratio of 3:1; the expansion component is azodicarbonamide; the antifreeze component is ethylene glycol; the retarding component is composed of citric acid and sodium gluconate mixed in a mass ratio of 2:1; the rust-inhibiting component is calcium nitrite; and the stabilizing component is hydroxymethyl cellulose.

[0036] The preparation method of the heat source material is as follows:

[0037] S1. Soak the salt mud in water at a mass ratio of 1:10, stir at 100 r / min for 1 h, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0038] S2. Dry the filter residue at 105℃ to constant weight, then heat it in a high-temperature furnace to 350℃ at 10℃ / min and hold for 3h, then heat it to 850℃ and hold for 3h, then continue to heat it to 1200℃ and hold for 4h, and then cool it to obtain the calcined product.

[0039] S3. After adding sodium tripolyphosphate to the calcined product in step S2, the product is ground. Then, melamine is added and ground again. The mass of sodium tripolyphosphate is 0.25% of the calcined product, and the mass of melamine is 0.8% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20%, and powder is obtained.

[0040] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 4:1 to obtain the heat source material.

[0041] Example 2

[0042] This embodiment provides a negative temperature grouting material for ducts, the raw materials of which include the following components in parts by weight: 350 parts of cementitious material, 650 parts of heat source material, 3 parts of water-reducing component, 1 part of expansion component, 100 parts of antifreeze component, 1 part of retarding component, 20 parts of rust-inhibiting component, 0.2 parts of stabilizing component, and 280 parts of water.

[0043] The cementitious material is composed of silicate cement, mineral powder, and silica fume mixed in a mass ratio of 40:5:1; the water-reducing component is composed of polycarboxylate superplasticizer and naphthalene-based superplasticizer mixed in a mass ratio of 7:1; the expansion component is azodicarbonamide; the antifreeze component is ethylene glycol; the retarding component is composed of citric acid and sodium gluconate mixed in a mass ratio of 2:1; the rust-inhibiting component is sodium benzoate; and the stabilizing component is hydroxymethyl cellulose.

[0044] The preparation method of the heat source material is as follows:

[0045] S1. Soak the salt mud in water at a mass ratio of 1:20, stir at 200 r / min for 1 hour, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0046] S2. Dry the filter residue at 110℃ to constant weight, then heat it in a high-temperature furnace to 500℃ at 10℃ / min and hold for 2 hours, then heat it to 900℃ and hold for 2 hours, then continue to heat it to 1300℃ and hold for 4 hours, and then cool it to obtain the calcined product.

[0047] S3. After adding sodium tripolyphosphate to the calcined product in step S2, the product is ground. Then, melamine is added and ground again. The mass of sodium tripolyphosphate is 0.5% of the calcined product, and the mass of melamine is 0.5% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20%, and powder is obtained.

[0048] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 2:1 to obtain the heat source material.

[0049] Example 3

[0050] This embodiment provides a negative temperature grouting material, the raw materials of which include the following components in parts by weight: 500 parts of cementitious material, 500 parts of heat source material, 7 parts of water-reducing component, 3 parts of expansion component, 140 parts of antifreeze component, 3 parts of retarding component, 10 parts of rust-inhibiting component, 0.8 parts of stabilizing component, and 260 parts of water.

[0051] The cementitious material is composed of silicate cement, mineral powder, and silica fume mixed in a mass ratio of 30:2:1; the water-reducing component is composed of polycarboxylate superplasticizer and naphthalene-based superplasticizer mixed in a mass ratio of 3:1; the expansion component is azodicarbonamide; the antifreeze component is ethylene glycol; the retarding component is composed of citric acid and sodium gluconate mixed in a mass ratio of 2:1; the rust-inhibiting component is calcium nitrite; and the stabilizing component is hydroxymethyl cellulose.

[0052] The preparation method of the heat source material is as follows:

[0053] S1. Soak the salt mud in water at a mass ratio of 1:10, stir at 100 r / min for 1 h, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0054] S2. Dry the filter residue at 110℃ to constant weight, then heat it in a high-temperature furnace to 350℃ at 10℃ / min and hold for 3h, then heat it to 850℃ and hold for 3h, then continue to heat it to 1100℃ and hold for 4h, and then cool it to obtain the calcined product.

[0055] S3. After adding sodium tripolyphosphate to the calcined product in step S2, the product is ground. Then, melamine is added and ground again. The mass of sodium tripolyphosphate is 0.1% of the calcined product, and the mass of melamine is 1% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20%, and powder is obtained.

[0056] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 6:1 to obtain the heat source material.

[0057] Comparative Example 1

[0058] The negative temperature grouting material in this comparative example is basically the same as that in Example 1, except that the heat source material is sulfoaluminate cement.

[0059] Comparative Example 2

[0060] The negative temperature grouting material in this comparative example is basically the same as that in Example 1, except that the preparation method of the heat source material is as follows:

[0061] S1. Soak the salt mud in water at a mass ratio of 1:10, stir at 100 r / min for 1 h, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0062] S2. Dry the filter residue at 105℃ to constant weight, then heat it in a high-temperature furnace to 350℃ at 10℃ / min and hold for 3h, then heat it to 850℃ and hold for 3h, then continue to heat it to 1200℃ and hold for 4h, and then cool it to obtain the calcined product.

[0063] S3. Melamine is added to the calcined product in step S2 and then ground. The mass of melamine is 0.8% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20% to obtain powder.

[0064] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 4:1 to obtain the heat source material.

[0065] Compared to Example 1, sodium tripolyphosphate was not added during the grinding process in step S3 of this comparative example.

[0066] Comparative Example 3

[0067] The negative temperature grouting material in this comparative example is basically the same as that in Example 1, except that the preparation method of the heat source material is as follows:

[0068] S1. Soak the salt mud in water at a mass ratio of 1:10, stir at 100 r / min for 1 h, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0069] S2. Dry the filter residue at 105℃ to constant weight, then heat it in a high-temperature furnace to 350℃ at 10℃ / min and hold for 3h, then heat it to 850℃ and hold for 3h, then continue to heat it to 1200℃ and hold for 4h, and then cool it to obtain the calcined product.

[0070] S3. After adding sodium tripolyphosphate to the calcined product in step S2, the product is ground. The mass of sodium tripolyphosphate is 0.25% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20%, and powder is obtained.

[0071] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 4:1 to obtain the heat source material.

[0072] Compared to Example 1, no melamine was added during the grinding process in step S3 of this comparative example.

[0073] Comparative Example 4

[0074] The negative temperature grouting material in this comparative example is basically the same as that in Example 1, except that the preparation method of the heat source material is as follows:

[0075] S1. Soak the salt mud in water at a mass ratio of 1:10, stir at 100 r / min for 1 h, filter, take the filter residue, and repeat the above operation until the filtrate does not produce a precipitate when titrated with silver nitrate solution.

[0076] S2. Dry the filter residue at 105℃ to constant weight, then heat it in a high-temperature furnace to 350℃ at 10℃ / min and hold for 3h, then heat it to 850℃ and hold for 3h, and then cool it to obtain the calcined product.

[0077] S3. After adding sodium tripolyphosphate to the calcined product in step S2, the product is ground. Then, melamine is added and ground again. The mass of sodium tripolyphosphate is 0.25% of the calcined product, and the mass of melamine is 0.8% of the calcined product. The product is ground until the residue on an 80μm square hole sieve is ≤20%, and powder is obtained.

[0078] S4. Mix the powder from step S3 with sulfoaluminate cement at a mass ratio of 4:1 to obtain the heat source material.

[0079] Compared with Example 1, the calcination at 1200°C was omitted in step S2 of this comparative example.

[0080] Test case

[0081] The performance of the grouting materials in the examples and comparative examples was tested, and the test results are shown in Table 1. Test methods: Flowability test was conducted according to Appendix A of "Grouting Materials for Prestressed Ducts in Highway Engineering" (JT / T 946-2022); setting time test was conducted according to "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement" (GB / T 1346-2011); mechanical properties were conducted according to "Test Methods for Strength of Cement Mortar (ISO Method)" (GBT 17671-2021); free expansion rate test was conducted according to Appendix B of "Grouting Materials for Prestressed Ducts in Highway Engineering" (JT / T 946-2022); restricted expansion rate test was conducted according to "Concrete Expansion Agent" (GB / T 23439-2017).

[0082] Table 1 Performance results of grouting materials

[0083]

[0084]

[0085] As can be seen from the results in Table 1, compared with the comparative examples, the grouting materials of Examples 1 to 3 of the present invention have high fluidity and moderate setting time under negative temperature conditions, and at the same time have excellent mechanical properties. The early and late strengths can meet the requirements of practical applications.

[0086] Compared to Example 1, the heat source material in Comparative Example 1 was entirely sulfoaluminate cement. On the one hand, since the heat source material was entirely sulfoaluminate cement, the ratio of sulfoaluminate cement to silicate cement in the cementitious material was approximately 60:40. Under this ratio, sulfoaluminate cement released a large amount of heat of hydration, and the two types of cement reacted violently. The entire grout reached final setting within 1 hour, at which point the retarder could not delay the setting. At the same time, the hydration of sulfoaluminate cement was almost complete within 3 days. At this point, the mechanical properties of the grouting material were mainly provided by a portion of silicate cement and the vast majority of sulfoaluminate cement. On the other hand, as the curing time increased, the heat source material could not provide heat in the middle and later stages, making it difficult for silicate cement to hydrate. Furthermore, the strength of sulfoaluminate cement decreased in the middle and later stages, resulting in a significant reduction in the mechanical properties of the grouting material in the middle and later stages.

[0087] This invention adds sodium tripolyphosphate during the preparation of the heat source material. Sodium tripolyphosphate coats and embeds itself on the surfaces of calcium oxide and magnesium oxide, essentially coating them with a "film," thus enabling calcium oxide to serve as a mid-stage heat source. In contrast to Example 1, Comparative Example 2 did not add sodium tripolyphosphate during the preparation of the heat source material. Calcium oxide reacts with water prematurely, resulting in complete reaction in the early stages. This not only releases a large amount of heat, shortening the initial setting time and reducing flow properties, but more importantly, it fails to provide a heat source during the mid-stage hydration of the cementitious material. This leads to a decrease in the mid-stage mechanical properties of the grouting material and even affects the development of its later strength.

[0088] Compared with Example 1, Comparative Example 3 did not add melamine to the heat source material, and the fluidity of the grouting material decreased. This shows that the heat source material of the present invention can not only release heat in stages to maintain the entire hydration process of the cementitious material, but also improve the fluidity of the grouting material.

[0089] Compared to Example 1, Comparative Example 4 lacked calcination at 1200℃, resulting in a significant increase in the activity of magnesium oxide, which could hydrate completely in 3 days. Consequently, it could not provide a heat source in the later stages of cementitious material hydration. This invention aims to use magnesium oxide as a later-stage heat source, releasing heat slowly to maintain the temperature of the slurry system, allowing the silicate cement to continue hydrating, and thus ensuring the development of the later-stage strength of the grouting material. Therefore, the absence of a 1200℃ calcination temperature will lead to a decrease in the later-stage strength of the grouting material.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A negative temperature grouting material, characterized in that, The components include the following parts by weight: 350-500 parts of cementitious material, 500-650 parts of heat source material, 3-7 parts of water-reducing component, 0.5-3 parts of expansion component, 100-140 parts of antifreeze component, 1-3 parts of retarding component, 10-20 parts of rust-inhibiting component, and 0.2-0.8 parts of stabilizing component. The method for preparing the heat source material includes the following steps: S1. Remove chloride ions from the salt mud to obtain filter residue; S2. Dry the filter residue, then keep it at 350-500℃ for 2-6 hours, raise the temperature to 850-900℃ and keep it at 2-6 hours, continue to raise the temperature to 1100-1300℃ and keep it at 3-6 hours, and then cool to obtain the calcined product. S3. Sodium tripolyphosphate and melamine are added to the calcination product of step S2, and then the product is ground and sieved to obtain powder. S4. Mix the powder from step S3 with sulfoaluminate cement to obtain the heat source material.

2. The negative temperature channel grouting material according to claim 1, characterized in that, In step S3, the mass of sodium tripolyphosphate is 0.1% to 0.5% of the calcined product, and the mass of melamine is 0.5% to 1% of the calcined product.

3. The negative temperature channel grouting material according to claim 1, characterized in that, In step S3, the powder is ground until the residue on an 80μm square-hole sieve is less than 20%.

4. The negative temperature channel grouting material according to claim 1, characterized in that, In step S4, the mass ratio of the powder to the sulfoaluminate cement is (2-6):

1.

5. The negative temperature channel grouting material according to claim 1, characterized in that, The mass fraction of NaCl in the salt mud is less than 2.5%. The specific operation for removing chloride ions from the salt mud in step S1 is as follows: Soak the salt mud in water, filter it, and take the filter residue. Repeat the above operation until no precipitate is produced when the filtrate is titrated with silver nitrate solution.

6. The negative temperature channel grouting material according to claim 1, characterized in that, The cementing materials include silicate cement, mineral powder, and silica fume.

7. The negative temperature channel grouting material according to claim 1, characterized in that, The water-reducing components include a polycarboxylate water-reducing agent and a naphthalene-based water-reducing agent in a mass ratio of (3-7):

1.

8. The negative temperature channel grouting material according to claim 1, characterized in that, The retarding component includes citric acid and sodium gluconate; the rust-inhibiting component includes at least one of calcium nitrite, sodium benzoate, ammonium heptamolybdate, sodium molybdate, and sodium hexametaphosphate; and the stabilizing component is cellulose ether or starch ether.

9. The negative temperature channel grouting material according to claim 1, characterized in that, The expanding component is azodicarbonamide.

10. A method for preparing a negative temperature grouting material according to any one of claims 1 to 9, characterized in that, The steps are as follows: Mix the cementitious material, heat source material, water-reducing component, expansion component, antifreeze component, retarding component, rust-inhibiting component and stabilizing component evenly, add water accounting for 26% to 28% of the total mass of cementitious material and heat source material and stir evenly to obtain the final product.

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