A magnesium silicate cementing material, its preparation method and use

Abstract

This invention belongs to the field of deep-earth engineering materials technology, and specifically relates to a magnesium silicate cementitious material, its preparation method, and its application. The raw materials for preparing the magnesium silicate cementitious material of this invention include quartz powder, magnesium hydroxide, and water; the molar ratio of magnesium to silicon in the raw materials is (0.75-1.5):1. This invention prepares a gel material by using specific magnesium hydroxide combined with quartz powder and water, and by precisely controlling the Mg / Si molar ratio to (0.75-1.5):1, enabling the system to stably form a cementitious structure dominated by amorphous hydrated magnesium silicate (M-S-H) gel under high-temperature conditions. This effectively avoids the high-temperature phase transformation problem of C-S-H gel in traditional silicate cement, as well as the crystallization problem of hydration products under high-temperature conditions, fundamentally improving the structural stability of the material under high-temperature environments, while also increasing the compressive strength of the material.

Description

Technical Field

[0001] This invention belongs to the field of deep earth engineering materials technology, and specifically relates to a magnesium silicate cementitious material, its preparation method and application. Background Technology

[0002] In the development of deep oil and gas resources and geothermal resources, the annular temperature of deep wells, ultra-deep wells, and geothermal wells often reaches above 150℃, and in some well conditions even exceeds 200℃. The core hydration product of traditional silicate oil well cement is hydrated calcium silicate (CSH) gel, which easily crystallizes at high temperatures above 110℃, transforming into α-C2SH with high density, low surface area, and weak strength. The original cementitious structure is destroyed, and the microstructure deteriorates, leading to an increase in the pore size and porosity of the cement matrix, resulting in a decrease in strength and ultimately causing the failure of zone isolation.

[0003] In silica-rich oil well cement systems, reducing the calcium-silica ratio can promote the formation of relatively stable minerals such as tobermorite at around 150°C, thus improving high-temperature performance to some extent. However, as the temperature further increases to 180°C and above, tobermorite may still transform into crystalline phases such as hard silicate, accompanied by problems such as coarsening of the pore structure. At 200°C and above, these degradation phenomena become more pronounced, thereby affecting the structural stability and long-term service performance of the cement paste.

[0004] Studies have shown that introducing high-temperature stabilizers such as quartz sand, microsilica, and nano-silica into silicate oil well cement systems, along with additives such as high-temperature reinforcing agents, retarders, and fluid loss reducers, can improve the mechanical properties and stability of cement slurry under high-temperature conditions. This technology reduces the calcium-silica ratio, generating relatively stable calcium silicate minerals such as tobermorite during hydration, thereby mitigating to some extent the performance degradation caused by the transformation of hydrated calcium silicate to a lower-strength phase at high temperatures.

[0005] However, in practical engineering applications, the above-mentioned technical solutions still have the following shortcomings: 1) These technical solutions are still based on silicate cement systems, and their performance improvement depends on the control of hydration products, failing to fundamentally avoid the problem of further phase transformation of CSH under high-temperature conditions. When the temperature exceeds 180℃ and the curing time is prolonged, tobermorite may still transform into hard calcium silicate, leading to a decrease in the stability of the material structure. 2) It usually relies on the synergistic effect of multiple admixtures to achieve high-temperature resistance, resulting in a relatively complex system composition and certain requirements for mix design and usage conditions. 3) Under long-term high-temperature conditions, the cement stone is still prone to coarsening of the pore structure and enhanced connectivity, manifested as increased porosity and permeability, thereby weakening the sealing integrity of the cement sheath and affecting the long-term safe service of the wellbore.

[0006] Therefore, developing a novel cementing material system that can form a stable structure under high-temperature conditions and does not undergo adverse crystallization reactions is of great significance in order to fundamentally improve the high-temperature stability of cementing materials. Summary of the Invention

[0007] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a magnesium silicate gelling material that does not undergo phase change at high temperatures and has good structural stability, thereby effectively avoiding the high-temperature phase change problem of CSH gel in traditional silicate systems; it also has good compressive strength.

[0008] The inventive concept of this invention: The raw materials for preparing the magnesium silicate cementitious material of this invention include quartz powder, magnesium hydroxide, and water; in the raw materials for preparing the magnesium silicate cementitious material, the molar ratio of magnesium to silicon is (0.75-1.5):1.

[0009] This invention prepares a gel material using specific magnesium hydroxide combined with quartz powder and water. By precisely controlling the Mg / Si molar ratio to (0.75-1.5):1, the system forms a gel structure dominated by amorphous hydrated magnesium silicate (MSH) gel under high-temperature conditions. This helps ensure the structural stability of the material at high temperatures and effectively avoids the crystallization problem of hydration products in traditional silicate cement under high-temperature conditions. Simultaneously, it exhibits low porosity and good compressive strength.

[0010] Therefore, a first aspect of the present invention provides a magnesium silicate cementing material.

[0011] Specifically, the raw materials for preparing the magnesium silicate cementitious material include quartz powder, magnesium hydroxide, and water; In the raw materials for preparing the magnesium silicate cementitious material, the molar ratio of magnesium to silicon is (0.75-1.5):1.

[0012] Specifically, by rationally limiting the molar ratio of magnesium to silicon, a gel structure dominated by amorphous hydrated magnesium silicate (MSH) gel can be formed. Furthermore, different magnesium-to-silicon ratios have a regulatory effect on material properties. Materials with a Mg / Si molar ratio of 0.75 exhibit higher compressive strength, while materials with a Mg / Si molar ratio of 1.5 show lower porosity and superior structural characteristics (such as a gel structure dominated by amorphous hydrated magnesium silicate and a continuous gel matrix) in some tests. These properties can be adjusted according to different well conditions.

[0013] Preferably, the raw materials for preparing the magnesium silicate cementitious material include 100 parts of quartz powder and 73.0-145.6 parts of magnesium hydroxide, by weight.

[0014] Preferably, the ratio of the mass of the water to the sum of the masses of the quartz powder and magnesium hydroxide is (0.4-0.6):1; for example, 0.4:1, 0.5:1, 0.6:1, etc.

[0015] Specifically, variations in the water-to-solid ratio within the range of 0.4-0.6 have a certain impact on the fluidity and mechanical properties of the slurry, but within this range, they do not change the gelation structure of the system, which is dominated by MSH gel.

[0016] Preferably, the quartz powder has a fineness of 900-1100 mesh.

[0017] Preferably, the mass content of SiO2 in the quartz powder is >99%.

[0018] Preferably, the true density of the quartz powder is 2.64-2.69 g / cm³. 3 More preferably, the true density of the quartz powder is 2.6847 g / cm³. 3 .

[0019] Preferably, the true density of the magnesium hydroxide is 2.36-2.41 g / cm³. 3 More preferably, the true density of the magnesium hydroxide is 2.4019 g / cm³. 3 .

[0020] Specifically, the magnesium hydroxide is reagent-grade analytical grade magnesium hydroxide.

[0021] Preferably, the magnesium silicate gelling material comprises amorphous hydrated magnesium silicate gel.

[0022] A second aspect of the present invention provides a method for preparing the magnesium silicate cementitious material described in the first aspect of the present invention.

[0023] Specifically, the preparation method of the magnesium silicate cementitious material includes the following steps: Quartz powder, magnesium hydroxide, and water are mixed to obtain a slurry, which is then cured to produce the final product.

[0024] Preferably, the quartz powder and magnesium hydroxide are first dry-mixed for 2-3 minutes, and then mixed with water.

[0025] Preferably, the mixing includes a first stage of stirring and a second stage of stirring; the first stage of stirring has a rotation speed of 2800-3200 rpm and a stirring time of 4-8 min; the second stage of stirring has a rotation speed of 3800-4200 rpm and a stirring time of 2-4 min.

[0026] Specifically, first stir at low speed to fully wet the powder, then stir at high speed to obtain a uniformly dispersed slurry.

[0027] Preferably, the slurry is placed in a mold and cured in a high-temperature and high-pressure curing autoclave.

[0028] Preferably, the curing temperature is 150-220℃; for example, temperatures of 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, etc.

[0029] Preferably, the maintenance pressure is 20-22 MPa; for example, the pressure is 20 MPa, 21 MPa, 22 MPa, etc.

[0030] Preferably, the curing time is 42-54 hours; for example, 42 hours, 43 hours, 44 hours, 45 hours, 46 hours, 47 hours, 48 ​​hours, 49 hours, 50 hours, 51 hours, 52 hours, 53 hours, 54 hours, etc.

[0031] Specifically, this invention, combined with curing conditions, can form a gel structure mainly composed of amorphous MSH gel after hydration at 150-220℃, without obvious crystalline silicate hydration products, thus achieving stable generation of amorphous MSH gel, which is beneficial to ensuring the structural stability of the material under high temperature environment.

[0032] A third aspect of the present invention provides an application of the magnesium silicate cementitious material described in the first aspect of the present invention in deep earth engineering.

[0033] Specifically, the main phase of the magnesium silicate cementitious material is amorphous hydrated magnesium silicate gel, which can be used as a high-temperature cementing stone in deep-earth engineering. Its strength remains stable with increasing temperature in high-temperature engineering at 150-220℃, meeting the structural stability requirements of materials under high-temperature conditions in deep-earth engineering.

[0034] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) This invention uses a specific magnesium hydroxide combined with quartz powder and water to prepare a gel material, and by precisely controlling the Mg / Si molar ratio to (0.75-1.5):1, the system can stably form a gel structure mainly composed of amorphous hydrated magnesium silicate (MSH) gel under high temperature conditions, effectively avoiding the high temperature phase transformation problem of CSH gel in traditional silicate cement and the crystallization problem of hydration products under high temperature conditions, fundamentally improving the structural stability of the material under high temperature environment, and at the same time improving the compressive strength of the material.

[0035] (2) By adjusting the magnesium-silicon molar ratio, the present invention achieves synergistic optimization of the microstructure and macroscopic properties of the material. While ensuring high compressive strength, it exhibits superior structural features such as low porosity, a gel structure dominated by amorphous hydrated magnesium silicate, and a continuous gel matrix, thus demonstrating the controllability of the material properties.

[0036] (3) The material of the present invention exhibits a stable phase structure and certain mechanical properties under high temperature conditions, which is beneficial to improving the structural stability of the material under high temperature conditions, thus providing a reference for the design of high temperature cementing materials. Attached Figure Description

[0037] Figure 1 The X-ray diffraction patterns of the magnesium silicate cementitious materials in Examples 1-4 of this invention are shown below. Figure 2 The X-ray diffraction patterns of the magnesium silicate cementitious materials in Examples 5-10 of this invention are shown below. Figure 3 The X-ray diffraction patterns of the magnesium silicate cementitious materials of Comparative Examples 1-2 of this invention are shown below. Figure 4 This is a scanning electron microscope image of the magnesium silicate cementitious material of Example 4 of the present invention; Figure 5 This is a scanning electron microscope image of the magnesium silicate cementitious material of Example 8 of the present invention; Figure 6 The cumulative pore volume distribution diagrams are shown for the magnesium silicate cementitious materials in Examples 1-8 of this invention. Detailed Implementation

[0038] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0039] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0040] Example 1 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 73.0 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0041] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 150℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0042] Example 2 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 73.0 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0043] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 180℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0044] Example 3 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 73.0 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0045] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0046] Example 4 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 73.0 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0047] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 220℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0048] Example 5 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 146 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0049] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 150℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0050] Example 6 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 145.6 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0051] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 180℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0052] Example 7 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 145.6 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0053] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0054] Example 8 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 145.6 parts of magnesium hydroxide, and water with a water-to-solid mass ratio of 0.5.

[0055] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 220℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0056] Example 9 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 97 parts of magnesium hydroxide (Mg / Si molar ratio of 1:1), and water with a water-to-solid mass ratio of 0.5.

[0057] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0058] Example 10 This embodiment provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 121 parts of magnesium hydroxide (Mg / Si molar ratio of 1.25), and water with a water-to-solid mass ratio of 0.5.

[0059] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0060] Comparative Example 1 This comparative example is used to verify the material properties under the condition that the magnesium-silicon molar ratio is 0.5.

[0061] This comparative example provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 48.5 parts of magnesium hydroxide (Mg / Si molar ratio of 0.5:1), and water with a water-to-solid mass ratio of 0.5.

[0062] This embodiment also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0063] Comparative Example 2 This comparative example provides a magnesium silicate cementitious material, which, by weight, is composed of the following raw materials: 100 parts of quartz powder, 100 parts of magnesium oxide (Mg / Si molar ratio of 1.5:1), and water with a water-to-solid mass ratio of 0.5.

[0064] This comparative example also provides a method for preparing the above-mentioned magnesium silicate cementitious material, including the following steps: (1) Dry mix quartz powder and magnesium hydroxide for 2 minutes, then place them together with water in a high-speed stirring device; first stir at a low speed of 3000 r / min for 6 minutes to fully wet the powder; then stir at a high speed of 4000 r / min for 3 minutes to obtain a highly uniform slurry; (2) The slurry was injected into a 50mm×50mm×50mm cubic mold and placed in a high-temperature and high-pressure curing kettle. It was cured at 200℃ and 21MPa for 48 hours, then demolded to obtain the product.

[0065] Performance testing 1. X-ray diffraction analysis X-ray diffraction analysis was performed on the magnesium silicate cementitious materials of Examples 1-10 and Comparative Examples 1-2. The X-ray diffraction patterns of the magnesium silicate cementitious materials of Examples 1-4 are shown below. Figure 1 As shown, the X-ray diffraction patterns of the magnesium silicate cementitious materials in Examples 5-10 are as follows. Figure 2 As shown, the X-ray diffraction patterns of the magnesium silicate cementitious materials in Comparative Examples 1-2 are as follows: Figure 3 As shown.

[0066] Depend on Figures 1-3 It can be seen that the product phase of Examples 1 and 5 is MSH gel + residual SiO2 + a small amount of unreacted Mg(OH)2; the product phase of Examples 2-4, 6, 9, and 10 is MSH gel + residual SiO2. The product phase of Examples 7-8 is pure MSH gel.

[0067] The product phase of Comparative Example 1 was mainly composed of raw material SiO2, with only trace amounts of MSH gel observed; the product phase of Comparative Example 2 consisted of MSH gel, characteristic peaks of raw material SiO2, and obvious intermediate product magnesium hydroxide, and the sample cracked due to volume expansion caused by the formation of magnesium hydroxide.

[0068] 2. Scanning electron microscopy observation The samples were freeze-dried (vacuum 0.3 mbar, temperature -40℃, for 48 h), and then the magnesium silicate cementitious materials of Examples 1-8 were observed by scanning electron microscopy. The scanning electron micrographs of the magnesium silicate cementitious materials of Examples 4 and 8 are shown below. Figure 4 , 5 As shown. By Figure 4 It can be seen that the microstructure of the gelling material in Example 4 is relatively uniform, forming a continuous gel matrix, without obvious macropores or through pores. Figure 5 It can be seen that the microstructure of the cementitious material in Example 8 shows an increase in foil-like structures, with no obvious large pores or through pores.

[0069] Meanwhile, the microstructure of the cementitious materials in Examples 1, 2, 3, 5, and 6 is similar to that in Example 4, i.e., the microstructure is relatively uniform, forming a continuous gel matrix, and no obvious macropores or through pores are observed. The microstructure of the cementitious material in Example 7 shows a foil-like structure, and no obvious macropores or through pores are observed.

[0070] 3. Compressive strength and porosity testing The compressive strength of the magnesium silicate cementitious materials in Examples 1-10 and Comparative Example 1 was tested according to GB / T 19139-2012 "Test Methods for Oil Well Cement". The nitrogen adsorption-desorption method (BET method) was used to test the magnesium silicate cementitious materials in Examples 1-8 using a BET adsorption instrument. The pore size distribution was obtained by analyzing the nitrogen adsorption-desorption isotherms, and the porosity of the materials was then calculated.

[0071] The compressive strength and porosity test results of the magnesium silicate cementitious materials are shown in Table 1. The cumulative pore volume distribution of the magnesium silicate cementitious materials in Examples 1-8 is shown in Table 1. Figure 6 As shown.

[0072] Table 1: Test results of compressive strength and porosity of magnesium silicate cementitious materials

[0073] In Table 1, "-" indicates that it was not tested. Also, in Comparative Example 2, the volume expansion caused by the formation of magnesium hydroxide led to the direct cracking of the sample after demolding, making it impossible to conduct a compressive strength test.

[0074] As can be seen from the XRD and SEM results and Table 1, within the range of Mg / Si = 0.75-1.5, different ratio systems can form a gel structure mainly composed of amorphous MSH gel at 150-220℃ and exhibit certain compressive strength, indicating that the magnesium-silicon molar ratio range defined by this invention has stable gelling ability.

[0075] In Comparative Example 1, the Mg / Si molar ratio was 0.5:1, which resulted in the product phase being mainly composed of raw material SiO2 with only trace amounts of MSH gel. Furthermore, the compressive strength was significantly lower than that of Examples 3, 7, 9, and 10 under the same curing conditions.

[0076] Comparative Example 2 used magnesium oxide, which resulted in the presence of the intermediate product magnesium hydroxide in the gel material, leading to sample cracking.

[0077] In summary, this invention prepares a gel material by using specific magnesium hydroxide combined with quartz powder and water, and by precisely controlling the Mg / Si molar ratio to (0.75-1.5):1, the system can stably form a gel structure mainly composed of amorphous hydrated magnesium silicate (MSH) gel under high temperature conditions. This effectively avoids the high-temperature phase transformation problem of CSH gel in traditional silicate cement and the crystallization problem of hydration products under high temperature conditions, fundamentally improving the structural stability of the material under high temperature environment, while also improving the compressive strength of the material.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A magnesium silicate cementitious material, characterized in that, The raw materials for preparing the magnesium silicate cementitious material include quartz powder, magnesium hydroxide, and water; In the raw materials for preparing the magnesium silicate cementitious material, the molar ratio of magnesium to silicon is (0.75-1.5):

1.

2. The magnesium silicate cementitious material according to claim 1, characterized in that, The raw materials for preparing the magnesium silicate cementitious material, by weight, include 100 parts of quartz powder and 73.0-145.6 parts of magnesium hydroxide.

3. The magnesium silicate cementitious material according to claim 2, characterized in that, The ratio of the mass of water to the sum of the masses of quartz powder and magnesium hydroxide is (0.4-0.6):

1.

4. The magnesium silicate cementitious material according to claim 1, characterized in that, The quartz powder has a fineness of 900-1100 mesh; And / or, the mass content of SiO2 in the quartz powder is >99%.

5. The magnesium silicate cementitious material according to claim 1, characterized in that, The magnesium silicate gelling material includes amorphous hydrated magnesium silicate gel.

6. The method for preparing the magnesium silicate cementitious material according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: Quartz powder, magnesium hydroxide, and water are mixed to obtain a slurry, which is then cured to produce the final product.

7. The preparation method according to claim 6, characterized in that, The mixing includes a first stage of stirring and a second stage of stirring; the first stage of stirring has a speed of 2800-3200 rpm and a stirring time of 4-8 min; the second stage of stirring has a speed of 3800-4200 rpm and a stirring time of 2-4 min.

8. The preparation method according to claim 6, characterized in that, The curing temperature is 150-220℃.

9. The preparation method according to claim 6, characterized in that, The curing pressure is 20-22 MPa; and / or the curing time is 42-54 h.

10. The application of the magnesium silicate cementitious material according to any one of claims 1-5 in deep earth engineering.

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