Highly permeable and high-strength nanometer silicon sol-based composite grouting material and preparation method thereof

Abstract

The application discloses a kind of high permeability high strength nano-silica sol-based composite grouting material and its preparation method, belong to grouting material technical field.It is constituted by the mixture of composition A and composition B with mass ratio of 4:5, composition A includes 35-38% of water by mass percentage, 61-64% of aluminate cement by mass percentage, 1% of modified additive;Composition B includes 96-99% of nano-silica sol by mass percentage, 1-4% of setting accelerator by mass percentage.Composition A is slowly added into composition B, and the adding time is not less than 1min, and the mixing temperature is 15-35 DEG C.The surface of slurry is not cracked, the stone rate of stone body is high, the volume shrinkage rate is low, the long-term volume stability is excellent, and the interface microstructure of slurry and mudstone is combined densely without gap, and the adhesion is excellent.

Description

Technical Field

[0001] This invention belongs to the field of grouting materials technology, specifically relating to a high-penetration, high-strength nano-silica sol-based composite grouting material and its preparation method. Technical Background

[0002] Muddy rock masses are widely present in deep underground engineering projects in my country. Due to their high clay mineral content, their tendency to swell, soften, and disintegrate upon contact with water easily leads to long-term large deformation and instability, severely affecting the structural safety and stability of underground engineering projects. Grouting can effectively block the dominant seepage channels of water in the surrounding rock fissures, improving the physical and mechanical properties of muddy rock masses. Extensive research and practice show that deep muddy rock masses exhibit multi-scale fissure distribution and micro-fissure development, and the effectiveness of grouting modification is closely related to the injectability of the grout material. Conventional cement-based grouting materials have particle sizes in the micrometer range, resulting in poor injectability and difficulty in achieving micro-fissure sealing and consolidation. Furthermore, the more developed the micropores in mudstone, the higher the surface free energy and the stronger the water adsorption, causing the cement-grouted rock mass to gradually soften, disintegrate, and weaken in strength. Therefore, the key to grouting reinforcement of multi-scale fissure mudstone is the consolidation of micropores; sealing and reinforcing the matrix micropores is the most fundamental and unavoidable problem in controlling large deformations of soft muddy rock.

[0003] Nanomaterials and nano-micro composite grouts have significant technical advantages and application prospects in the field of grouting and control of argillaceous rock masses. For example, ultrafine cement has higher injectability in small fissures than ordinary cement, but its high fineness and large specific surface area make it prone to agglomeration, requiring an increased water-cement ratio to reduce viscosity. Nano-silica sol, on the other hand, possesses outstanding characteristics such as nano-particle size, low viscosity, and high permeability, and has been widely applied internationally in groundwater protection and nuclear waste storage, but its strength is relatively low (<0.5 MPa). Using only one material for grouting has its drawbacks; therefore, a development trend in grouting materials is towards composite materials, utilizing the superposition effect of multiple components to overcome the performance deficiencies of a single material. Furthermore, because argillaceous rock masses contain numerous millimeter-micrometer-nanoscale fissures, it is difficult to achieve the sealing and reinforcement of multi-scale pores and fissures using a single-scale grout. Therefore, a nano-microscale, highly injectable, and high-strength composite grout is currently needed for gradient filling and consolidation of multi-scale pores and fissures in argillaceous rock masses. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a high-penetration, high-strength nano-silica sol-based composite grouting material and its preparation method. The steps are simple, the method is convenient, the grout surface does not crack, and the microstructure of the grout and mudstone interface is dense, void-free, and has excellent adhesion.

[0005] To achieve the above-mentioned technical objectives, the present invention provides a high-penetration, high-strength nano-silica sol-based composite grouting material, characterized in that it is composed of a mixture of composition A and composition B in a mass ratio of 4:5, wherein...

[0006] Composition A comprises 35-38% by mass of water, 61-64% by mass of aluminate cement, and 1% by mass of a modifier.

[0007] Composition B comprises 96-99% by weight of nano-silica sol and 1-4% by weight of coagulant.

[0008] Furthermore, the aluminate cement needs to meet the following requirements: Al2O3 mass percentage of 51-54%, CaO mass percentage of 35-37%, SiO2 mass percentage of 4-6%, and specific surface area ≥400m2 / kg.

[0009] Furthermore, the modified additive has the following weight composition ratio: 75-85 parts magnesium oxide, 5-10 parts calcium oxide, and 10-15 parts sodium silicate; wherein the mass purity of magnesium oxide is not less than 98%, the mass purity of calcium oxide is not less than 98%, and the mass purity of Na2O in sodium silicate is not less than 28.2%.

[0010] Furthermore, the nano-silica sol is an alkaline industrial silica sol, wherein the concentration of nano-silica is 10-30% and the average particle size does not exceed 20 nm.

[0011] Furthermore, the coagulant is a NaCl solution with a mass concentration of 8-10%.

[0012] A method for preparing a high-penetration, high-strength nano-silica sol-based composite grouting material includes the following steps:

[0013] (1) Mix the water in composition A with aluminate cement and modified admixture, and stir for no less than 3 minutes and at a stirring speed of no less than 500 rpm;

[0014] (2) Add the coagulant in composition B into the nano silica sol. While adding the coagulant, keep stirring continuously. After adding, the stirring time should not be less than 3 minutes and the stirring speed should not be less than 500 rpm.

[0015] (3) Mix the prepared composition A and composition B at a mass ratio of 4:5 and stir for 3-5 minutes to obtain nano-silica sol-based composite grouting material.

[0016] Furthermore, composition A is slowly added to composition B over a period of not less than 1 minute, and the mixing temperature is 15-35°C.

[0017] Beneficial effects: The nano-silica sol-based composite grouting material of the present invention, through the composite of nano-silica sol and special aluminate cement, forms a composite grouting material with a crack width as low as 50nm and a 3-day compressive strength ≥10MPa, which has nano-micron dual-level particle size distribution characteristics. It fully utilizes the beneficial characteristics of ultra-high injectability of nano-silica sol and high strength of cement grout. The injectability is more than 100 times higher than that of conventional cement grout, and it can simultaneously achieve the dual effects of shallow large crack reinforcement and deep micro crack sealing.

[0018] The silica sol-based composite grouting material disclosed in this invention, through a three-stage compounding of magnesium oxide, calcium oxide, and sodium silicate, significantly improves the stability of the grout and the aggregate, achieving surface-free grout, an aggregate consolidation rate of ≥97.5%, a volume shrinkage rate of ≤0.5%, and excellent long-term volume stability. The grout-mudstone interface exhibits a dense, void-free microstructure with excellent adhesion, making it particularly suitable for grouting and seepage prevention reinforcement projects in deep argillaceous fractured rock masses. The gelation time of this material can be controlled within 0.1–1.5 hours by adjusting the proportion of the accelerator added, according to the grouting time requirements of different projects.

[0019] The preparation method of the silica sol-based composite grouting material of the present invention is simple and easy to implement, with low requirements for production equipment and personnel, short production cycle, and all raw materials are non-polluting, non-toxic, and environmentally friendly, comparable to ultrafine cement. Attached Figure Description

[0020] Figure 1 This is a diagram showing the surface properties of the grout of the nano-silica sol-based composite grouting material in an embodiment of the present invention.

[0021] Figure 2 This is a nanoscale particle size distribution diagram of the nano-silica sol-based composite grouting material in an embodiment of the present invention;

[0022] Figure 3 This is a micron-sized particle size distribution diagram of the nano-silica sol-based composite grouting material in the embodiments of the present invention;

[0023] Figure 4 This is a microstructure diagram of the solidified body of the nano-silica sol-based composite grouting material in the embodiments of the present invention;

[0024] Figure 5 Microscopic structure diagram of the bonding between the stone body and mudstone interface of the material of this invention; (a) is a 2000x magnified view, (b) is a 5000x magnified view, and (c) is an 8000x magnified view.

[0025] Figure 6 This is a diagram showing the shrinkage and cracking of the stone body in the nano-silica sol-based composite grouting material in an embodiment of the present invention. Detailed Implementation

[0026] An embodiment of the present invention will be further described below with reference to the accompanying drawings:

[0027] Example 1

[0028] A high-strength nano-silica sol-based composite grouting material is composed of a mixture of composition A and composition B. Composition A includes 280g of water, 512g of aluminate cement, 6.8g of magnesium oxide, 0.4g of calcium oxide, and 0.8g of sodium silicate; composition B includes 990g of nano-silica sol and 10g of NaCl solution.

[0029] The aluminate cement contains 51-54% Al₂O₃, 35-37% CaO, and 4-6% SiO₂ by mass, with a specific surface area ≥400 m² / kg. Magnesium oxide and calcium oxide have a purity of at least 98%, and sodium silicate contains at least 28.2% Na₂O by mass. The nano-silica sol is an alkaline industrial silica sol with a silica concentration of 30% and an average particle size of 10 nm. The NaCl solution has a mass concentration of 10%.

[0030] The preparation method of the above material includes the following steps:

[0031] (1) Mix the water in composition A with aluminate cement and modified admixture, stir for 3 minutes at a stirring speed of 500 rpm.

[0032] (2) Add the coagulant accelerator in composition B into the nano silica sol while continuously stirring. After the addition is complete, stir for 3 minutes at a stirring speed of 500 rpm.

[0033] (3) Slowly add the prepared composition A into composition B for 1 minute, mix at 20°C, and stir for 3 minutes to obtain nano-silica sol-based composite grouting material.

[0034] Example 2

[0035] A high-strength nano-silica sol-based composite grouting material is composed of a mixture of composition A and composition B. Composition A includes 296g of water, 496g of aluminate cement, 6.4g of magnesium oxide, 0.56g of calcium oxide, and 1.04g of sodium silicate; composition B includes 980 nano-silica sol and 20g of NaCl solution.

[0036] The aluminate cement contains 51-54% Al₂O₃, 35-37% CaO, and 4-6% SiO₂ by mass, with a specific surface area ≥400 m² / kg. Magnesium oxide and calcium oxide have a purity of at least 98%, and sodium silicate contains at least 28.2% Na₂O by mass. The nano-silica sol is an alkaline industrial silica sol with a silica concentration of 30% and an average particle size of 10 nm. The NaCl solution has a mass concentration of 10%.

[0037] The preparation method of the above material includes the following steps:

[0038] (1) Mix the water in composition A with aluminate cement and modified admixture, stir for 3 minutes at a stirring speed of 500 rpm.

[0039] (2) Add the coagulant accelerator in composition B into the nano silica sol while continuously stirring. After the addition is complete, stir for 3 minutes at a stirring speed of 500 rpm.

[0040] (3) Slowly add the prepared composition A into composition B for 1 minute, mix at 20°C, and stir for 3 minutes to obtain nano-silica sol-based composite grouting material.

[0041] Example 3

[0042] A high-strength nano-silica sol-based composite grouting material is composed of a mixture of composition A and composition B. Composition A includes 280g of water, 512g of aluminate cement, 6g of magnesium oxide, 0.8g of calcium oxide, and 1.2g of sodium silicate; composition B includes 970g of nano-silica sol and 30g of NaCl solution.

[0043] The aluminate cement contains 51-54% Al₂O₃, 35-37% CaO, and 4-6% SiO₂ by mass, with a specific surface area ≥400 m² / kg. Magnesium oxide and calcium oxide have a purity of at least 98%, and sodium silicate contains at least 28.2% Na₂O by mass. The nano-silica sol is an alkaline industrial silica sol with a silica concentration of 30% and an average particle size of 10 nm. The NaCl solution has a mass concentration of 10%.

[0044] The preparation method of the above material includes the following steps:

[0045] (1) Mix the water in composition A with aluminate cement and modified admixture, stir for 3 minutes at a stirring speed of 500 rpm.

[0046] (2) Add the coagulant accelerator in composition B into the nano silica sol while continuously stirring. After the addition is complete, stir for 3 minutes at a stirring speed of 500 rpm.

[0047] (3) Slowly add the prepared composition A into composition B for 1 minute, mix at 20°C, and stir for 3 minutes to obtain nano-silica sol-based composite grouting material.

[0048] Comparative Example 1

[0049] Same as Example 1, except that aluminate cement is replaced with silicate cement, and the composition contains 29.7g of water and 49.5g of silicate cement.

[0050] Comparative Example 2

[0051] Same as Example 1, except that the aluminate cement is replaced with sulfoaluminate cement, and the composition contains 29.7g of water and 49.5g of sulfoaluminate cement.

[0052] Comparative Example 3

[0053] Same as Example 1, except that aluminate cement is replaced with silicate cement, and the composition contains 280g of water and 512g of silicate cement.

[0054] Comparative Example 4

[0055] Same as Example 1, except that the aluminate cement is replaced with sulfoaluminate cement, and the composition contains 280g of water and 512g of sulfoaluminate cement.

[0056] Comparative Example 5

[0057] Same as Example 1, except that magnesium oxide is not added.

[0058] Comparative Example 6

[0059] Same as Example 1, except that calcium oxide is not added.

[0060] Comparative Example 7

[0061] Same as Example 1, except that sodium silicate is not added.

[0062] Testing showed that the nano-silica sol-based composite grouting materials prepared in Examples 1-3 exhibited uniform grout properties and did not shrink or crack. Figure 1 The slurry has high permeability, viscosity, and hardening rate, such as... Figure 2 and Figure 3As shown, the slurry exhibits a two-tiered particle size distribution between nanometer and micrometer sizes, with a minimum injectable crack width as low as 50 nm, more than 100 times that of cement slurry; its 3-day compressive strength is ≥10 MPa, more than 100 times that of nano-silica sol-bound stone, and its microstructure is dense and uniform. Figure 4 The microstructure of the bonding surface with mudstone is dense and without voids, such as Figure 5 As shown, Figure 5 The images shown are (a) at 2000x magnification, (b) at 5000x magnification, and (c) at 8000x magnification. The interface adhesion and sealing effect are excellent, which can meet the needs of grouting and seepage prevention reinforcement of muddy roadways / tunnels.

[0063] Table 1 shows a comparison of the performance of the nano-silica sol-based composite grouting materials prepared in Comparative Examples 1-3 with those in Example 1.

[0064] Table 1. Comparison of Performance of Nano-Silica Sol-Based Composite Grouting Materials

[0065] Case gel time / min Compressive strength / MPa Example 1 126 12.7 Comparative Example 1 4.2 0.8 Comparative Example 2 5.5 1.1 Comparative Example 3 ≤0.5 — Comparative Example 4 ≤0.5 —

[0066] As shown in Table 1, when aluminate cement is replaced with an equal weight of silicate cement and sulfoaluminate cement, the composite grout exhibits instantaneous solidification, with a gel time ≤0.5 min, and its strength cannot be measured. However, when the amount of silicate cement and sulfoaluminate cement added becomes 3% of the amount of nano-silica sol added, the composite grout finally has a workable time, and the measured strength is less than one-tenth of that in the example. This indicates that with the addition of silicate cement and sulfoaluminate cement, the workable time and compressive strength of the grout are far from meeting the engineering requirements.

[0067] The nano-silica sol-based composite grouting materials prepared in Comparative Examples 4-6 cannot meet the requirements of three-level compounding of modified admixtures, and generally exhibit uneven deformation of the stone surface leading to cracking, such as... Figure 6 As shown, problems such as overall volume shrinkage can cause the rock mass seepage prevention structure to fail after grouting, making it unable to meet the requirements of grouting seepage prevention and reinforcement for roadways / tunnels.

[0068] The above description of the embodiments is only intended to help understand the principles of the embodiments of the present invention; at the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A high-penetration, high-strength nano-silica sol-based composite grouting material, characterized in that: Composition A and composition B are prepared by mixing them in a mass ratio of 4:5, wherein, Composition A comprises 35-38% water by weight, 61-64% aluminate cement by weight, and 1% modifying admixture by weight. The modified admixture has the following weight composition: 75-85 parts magnesium oxide, 5-10 parts calcium oxide, and 10-15 parts sodium silicate. The magnesium oxide has a purity of not less than 98%, the calcium oxide has a purity of not less than 98%, and the sodium silicate contains Na₂O with a purity of not less than 28.2%. Composition B comprises 96-99% by weight of nano-silica sol and 1-4% by weight of coagulant; The preparation method includes the following steps: (1) Mix the water in composition A with aluminate cement and modified admixture, and stir for no less than 3 minutes and at a stirring speed of no less than 500 rpm; (2) Add the coagulant in composition B into the nano silica sol. While adding the coagulant, keep stirring continuously. After adding, the stirring time should not be less than 3 minutes and the stirring speed should not be less than 500 rpm. (3) Mix the prepared composition A and composition B at a mass ratio of 4:5 and stir for 3-5 minutes to obtain nano-silica sol-based composite grouting material.

2. The high-penetration, high-strength nano-silica sol-based composite grouting material according to claim 1, characterized in that, The aluminate cement needs to meet the following requirements: Al2O3 mass percentage 51~54%, CaO mass percentage 35~37%, SiO2 mass percentage 4~6%, and specific surface area ≥400m2 / kg.

3. The high-penetration, high-strength nano-silica sol-based composite grouting material according to claim 1, characterized in that, The nano-silica sol is an alkaline industrial silica sol, wherein the concentration of nano-silica is 10-30% and the average particle size does not exceed 20 nm.

4. The high-penetration, high-strength nano-silica sol-based composite grouting material according to claim 1, characterized in that, The coagulant is a NaCl solution with a mass concentration of 8-10%.

5. The high-penetration, high-strength nano-silica sol-based composite grouting material according to claim 1, characterized in that, Slowly add composition A to composition B over a period of not less than 1 minute, and mix at a temperature of 15-35°C.

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